I can see why some people might take unneeded amounts of time to play their hands. As you stated up there it is probably to test the patience of the other players. If you can get under their skin then they may focus less on the game or get distracted.

Those long hour games would be really frustating especially when you have bad cards with you. So i prefer to quit such games.

Well if you believe you are winning, it might be good to stretch the game out a bit longer. It makes the opponents have to wait and often times they will second guess themself.