[Kaeser]

Well I can't claim to know exactly why they play the way they do, but I have a theory. They like to see the showdown. They aren't interested in making money but they also don't want to feel stupid. If they bet and got raised then they'd have to have a hand to feel good about calling. As long as they just check they can decide your probably bluffing and call you all the way.

As to why that pisses you off so much. That's a little more complex. Give me a little info on why you think it bothers you so much to see them play this way. Do you take great pride in playing poker the "correct" way? Are you annoyed even when you aren't in the hand or only when they play that way against you?