The simple fact is that most miners are a combination of lazy, fickle, uninformed and just all round suspicious and seem to be unable to understand payout schemes, variance and luck no matter how much it's explained to them, and their care factor for things like security of the network, distributing the hashrate etc. etc. just isn't high enough to offset the fact that the primary thing they care about is profits. Then they do pseudo experiments ignoring all the things I said above and show a better payout at some random other pool for that day and they're lost for good.