I was on 2.50.something until fairly recently, and didn't notice much change when I updated to 2.51.26, so it does seem as if they don't bother you with the program update unless you really need it. (That's not to say that there isn't an important difference under the hood, but the website only has a warning to pre-2.5 users to get 2.5, so 2.51 doesn't seem particularly critical).
I think I prefer this, to be honest. McAfee was forever wanting a reboot after a program update, and I'll bet you most of those updates were completely pointless.