What if you think you sleep well now, but it turns out you can sleep so much better?
I'm not saying you will (I'm neither pro- nor anti-caffeine). But I am saying that unless you've tried it, you have no way of knowing. And I know lots of people who have improved their sleep in various ways, who thought they were sleeping normally/fine, and then discovered they actually hadn't been -- they just didn't know any better.
(And even if millions of people do something as a matter of culture, that doesn't mean it's good for your health. There are tons of cultural practices that are bad for health, or bad for a subset of the population.)