> But the goal of an encyclopedia is to inform people on things that it covers, isn't it?

Yes, but that implies filtering on all things that are false. And in this day and age, filtering truth is a very hard thing to do, so instead they set the bar a little higher at “a reputable source checked that it is indeed true”. As a result, there's plenty of things that are both true and well known to plenty of people that aren't on Wikipedia, but that's fine, and encyclopedia doesn't need to be exhaustive to be useful.

But on the flip side, if they didn't, it would soon be filled by tons of made up things fabricated for marketing reasons.