In single players game and small games you just play to enjoy or explore/discover, information is not a concern because you have no reason to break the sense of exploration and discovery for yourself. One of the problems with MMOs however, is the need to be on top. That you compete to be the best. And when people is willing to crunch numbers until they find a tiny extra amount of DPS, you can be damn sure they're willing to read everything before they experience it so they can maximize their efficiency and thereby be better than others who don't.