The problem isn't older men, the "problem" for many game developers (and possibly also gamers) is older women, both as playable and non-playable characters. Let's take a look at RE: On the male side, we have 40-something-year-old Chris in RE7, Leon who should also be pushing 40 by Vendetta, Wesker and Barry who were already "old" in RE1 and just got older, that fossil Spencer, Simmons, Quint and Keith (not sure about the latter, but Quint is certainly 40+), the singing maniac from Zero that eventually got himself a younger body, and several older-looking side characters like Chief Irons, President Benford, Enrico Marini, etc. Not that there aren't plenty of young men as well, but the games don't shy away from letting them age.
On the female side, we have 50-year-old Alex Wesker who doesn't have a single visible wrinkle or grey hair, Svetlana from Damnation, and 40ish-year-old Ada in RE6 who is probably only in the game because of Leon. Leon himself was paired with 24-year-old newcomer Helena instead of Claire or Jill, who would have been in their mid to late 30s at that point (and haven't been seen since even before that), and even Sherry was made to look younger than she really is, as if 26 was already too old for a woman. I guess with Sherry, they wanted to retain some of her childlike sweetness for the sake of memorability, but then they could have made Helena a bit older at least, and it's notable that Sheva is also only 23 next to 35-year-old Chris in RE5.
Looking at other long-running game franchises, we have Tomb Raider which was rebooted around the time the original Lara would have turned 40. Okay, we have Natla who is technically thousands of years old, but naturally doesn't look the part because she's immortal. The only female protagonist in the entire Silent Hill franchise is a 17-year-old girl, otherwise it's usually a middle-aged male protagonist surrounded by younger, attractive females. The Last of Us isn't revolutionary in that regard either, personally I would have found a Joel-aged woman paired with an Ellie-aged boy a lot more interesting, but I'm probably the only one.