Realistically most certainly applies to any RPG, including fantasy, sci-fi, or any other environment. No one, anywhere, any character, in any story ever told, simply stops developing... unless they are dead, of course. That is unrealistic. RPGs generally do not deal with aging, but they almost always deal with developing characters. Development is ongoing as long as a character, and we, are alive, no matter what environment any of us may exist within.
And fyi, I am in my upper 40s, thanks.

Well.... if we're going to go for realism, then many of your attributes should
decrease over time, after peaking at an age equivalent to about the late teens or early 20s. That's certainly the case with endurance and arguably with strength and even intelligence. Granted some attributes and many skills should continue to increase beyond that point, and potentially for a while beyond it, but virtually all of them will peak at a given point, which point is probably nothing even close to "100%." That's reality, and I would think that someone in their upper 40s (as I am as well), couldn't help but recognize that. I know for a fact that I have less endurance and less strength than I had years ago, and that I never had either the endurance or the strength of, for instance, a professional athlete, so I never had anything that might be even close to a "100" in either one, and there really was never a chance that I would, no matter how much I worked at it-- I just don't have the genes for that. I probably had something close to a "100" in intelligence in my prime, but even that has passed. My mind is a bit slower and a bit more "porous" than it used to be. That's okay-- it's just a part of aging. That's the reality. So certainly if we're going for "realism" in a game, the reality is that one character should maybe be able to reach something close to 100 in one or two or maybe three attributes and maybe a handful of skills, and that's it. Anything more than that is superhuman, and not by any stretch "realistic."
Just saying is all....
Frankly, I think it's pointless to play if you will stop leveling at 30 or anything else. In fact, many people seem to feel this way about RPGs as ArenaNet discovered when they put a level 20 cap in Guild Wars (and other MMO makers have discovered this, as well... that people want to keep leveling their characters, or it feels pointless to play the characters).
Not everyone, of course... but a good many people seem to feel this way, or there would not be so much effort to offer leveling beyond caps in games.
Broadly, with the proviso that dichotomies are insufficient at best, there seems to be two broad approaches to RPGs-- to ignore or limit character progression and just make one's way through the world, dealing with or even reveling in faults and flaws and quirks and shortcomings, or to shoot for perfection and set maximization as the goal toward which to strive. It seems to be two entirely different psychologies at play, and I sincerely doubt that anyone of either group will ever entirely understand the motivations of those of the other group.
As a side note, I would be willing to bet that this is a thing of which game developers are aware, and that part of the strategy to makig a successful game is to try to find a way to balance it so that both groups are pleased with the result. And some compromise is certainly necessary to do that, which compromise might well be the source of some of the issues that those of either group end up having with a particular game......
Just a stray thought, running through my porous mind......