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I am sometimes under the impression that a lot of people think rationality is Spock. You can read the link on an explanation of why that is not so.
No, usually, when rational folk talk about rationality, we talk about two things:
Something is epistemically rational if it helps form or stems from true beliefs.
Something is instrumentally rational if it helps achieve or is a consequence of achieving your goals.
So, basically, you're being rational when you find out true things, act on true things (and that includes changing your mind when you find out you're wrong) and optimally achieve your goals.
It's not that scary, is it? No, of course not. And it sheds some light on why Spock isn't rational at all: if he loses to Captain Kirk on 3D chess when Kirk is "intuitive" and "irrational," clearly the irrational one is captain Spock himself. But go read the link above to see a more thorough deconstruction of the trope.
Knowing that, why wouldn't you want to be rational? It's paradoxical: you would have to want to believe false things (and if you know they're false, then you obviously don't believe them) and want to foil your own achievements (and if you want to not achieve your goals, then your goal of failing at everything is effectively achieved).
When we play technical rationality games, when I discuss all these dozens of subjects about rationality, what I'm really doing is explaining techniques of finding truth and achieving goals.
Rationality is to win, systematically and frequently. It's, simply, the art of winning.
