+1
I also think there's this weird cultural fixation on fathers as actual caretakers. Oop, that wacky dad is trying to braid his daughter's hair!!! Whoa, that boy wants to kiss that dad's daughter!!
I remember a male friend posting in bafflement that he'd had multiple experiences where he was walking around doing errands with his daughter in a sling or whatever and people would come up to him and really sincerely be like "Good for you!". (And one time he overheard someone go "Ooh! Here comes that tasty daddy!" LOL). I don't think there's quite the cultural fascination with mothers (much less single mothers), and especially not with the relationships they have with their sons.
Father-child films often have the loss of the mother as an inciting incident which shifts responsibility for caretaking to the father and then they have to work out that new dynamic. If you lose a father I'm not saying that's not a loss (NOT AT ALL!) but chances are the mom was probably more of the primary caretaker, so the shift is in a different dynamic. As a teacher, people often make it a point to mention that a child is being raised by only their father, but it can be much longer before I learn that a child is being raised only by their mother. It's just seen as being more remarkable and interesting.
You know what's a good one, though, and a family film to boot? Rookie of the Year. She supports him in his athletic goals, keeps him from being exploited, and in the end they bond over realizing that she was a great baseball player and she gives him the advice he needs to be victorious.
In terms of the "new caretaker" dynamic I described with fathers, there are probably a few with foster mothers.