How come in Westerns, the police wait for villains to draw first?

I always notice this in westerns, the police or law officers, will always wait for the villains to draw their pistols first, before drawing theirs. Like in this example from Tombstone:



But you see it in other Western movies as well.

But when you watch movies set in more modern times, the police always have their guns drawn, and aimed and ready to go, when making arrests. Like in The Dark Knight, when they send in SWAT teams to make arrests, guns out and ready to go.

I am wondering, is there a reason why Westerns do it differently? Is it a stylistic choice to be different, or is it historical that the police wait for the villains to draw first back then compared to modern times? What do you think?

Probably so no one can argue they didn't shoot in self defense.

Also it's badass.

Maybe a customary thing for the western era also. Frowned upon to have a gun drawn - that’s yellow.

It's also fun to look to science fiction. In Blake's 7 for instance Avon will quite happily shoot an adversary in the back. Simple matter of self-preservation – why give them a chance ?

sometimes the police are the bad guys that draw first

In the case of the OK Corral, it was alleged that Wyatt Earp and his accomplices drew first. It’s been argued they were in fact lead by his older brother, Virgil. The lawman shooting first is really a Idea driven by the film directors to make keep the lawman viewed as the good guy.
Wyatt Earp doesn’t haven’t nearly a great reputation as the films have portrayed, mostly upon his insistence written in his autobiography, and the films that followed making him some sort of folk hero, but he was never the good guy in real life.
The veangence he exacted after Morgan Earps assassination did happen, and is a great starting point on how this destroys his myth. Him and several others really did hunt several cowboys down and murdered them without a warrant, and without a trial.
Yet nothing was ever done about it because he carried a badge iirc.
Carrying a badge allowed a lot of leeway in the West in regards to what one could get away with afterall.

Oh okay, cause if it was alleged that Earp and his accomplices drew first, I would assume so, since it's normal for police to have their guns drawn when making arrests, at least that is how it's often depicted.

I never saw Earp as the good guy in the movie Tombstone though, since it does show him go out and kill a bunch of the Cowboy gang without warnings, after the OK Corral battle. But the movie also portrays the legal system as broken and no court doesn't seem to want to prosecute the cowboys either, at least according to the movie.

Even more so, there are existing newspapers reports from that I cite this where it was claimed the victim said “Hold it!”
In an attempt to avoid trouble. The only guns drawn when approaching someone back were a shotgun, from I had read. Guns were to be holstered, but a shotgun was kept by your side, uncocked. To cock one was taken as a threat, and even to touch your gun while holstered, as if ready to draw, was enough to be deemed a threatening gesture.
Tombstone absolutely made him out to be a heroic figure, but so did other films before it such as “My Darling Clementine” which I have seen, and “Gunfight at the OK Corrall”, Which I have not.
The legal system was absolutely broken back then, particularly in the western states, which was why it was always referred to in modern times the Wild West. Of course, the East was no better, particularly New York with boss Tweed and their gangs. (As an aside, when “Gangs of New York” was released, I was quite interested in seeing his portrayal as I had been familiar with with reading about him in a history book in the library where I spent spare time during study hall)
In those times, most saw a badge as being above the law and some were even willing to use what extremes they saw fit to keep the peace, not so much as being the “bad guy” but in the belief that the ends justified the means. They often open fire before asking questions, or so it seemed to me.
For example, Pat Garret and his gang opening fire on Billy the Kids gang when they exited their hideout, Sheirff Brady and his posse killing Billy the Kids employer Sparking the war that followed, as well as the aforementioned Earp incidents.
It truly was a fascinating, albeit dangerous, time.

Because there's no black guys in westerns

I don't understand how Tombstone made him out to be a heroic figure because in the third act of the movie, there are two montage sequences that show him going around murdering cowboys without warning. Isn't that a more accurate, less heroic portrayal?

It is but it was glorified in a heroic light , much like most vigilantes as told today, and since the 7o’s. The whole buildup to it was fictionalized, as the Cowboys didn’t come looking for trouble when he first arrived due to his reputation as a lawman. It has been reported the Earps actually mistreated them. The film sets it up that he had no choice in the matter but to take the matter into his own hands and that the Cowboys were the aggressors throughout. You and I can agree it really wasn’t, but most people would feel he was.
He was never brought to justice over it, and the time he murdered Ike Clayton (I could be mistaken on the identity) at a railroad station, it was ruled justified despite no witnesses as I recall.

Oh okay, why don't they make a Wyatt Earp movie where he was more the antagonizer then?

Because it’s very much like the famous line from John Fords film “The Man who shot Liberty Valance”.
When the legend becomes fact, print the legend.

Oh okay, it's just not everyone has to listen to John Ford types of ideals, and westerns have come a long way since.

True, they don’t have to. But yet they do.
And regardless of how far westerns have come, it isn’t all that different from The Irishman. A former gangster gives an interview about his life and what crimes he committed, including murdering Hoffa, yet it is highly disputed for a number of reasons.
Wyatt Earp did much the same thing.
A tale about an alternative point of view a put him being the antagonist would be interesting, but I don’t see it happening due to waning interest in westerns these days.

I would say the difference really is the kind of films your talking about. Most westerns tend towards romantic heroism were as police dramas are more likely to be morally grey and so have the protagonists "shoot first".

This is true, and westerns had a actual hero they could use as their template, if not outright actual portrayal, that they could use. Even if his life was a highly fictionalization.