[RustyBrooks]

They want to get more money in the pot, essentially raising the stakes in a no limit game, because they are better than other people. [Edit: this is why decent players might do it. Gamblers do it to gamble] The reason the stakes are essentially raised is that in order to give proper pot odds (or deny pot odds, etc), a raiser now has to raise more to get the same effect.

In limit games this does not have the same effect, really, because it just makes it more profitable for people to chase. However, most people in limit games do not take the extra money into consideration and attempt to win it right away, so I like it when people straddle. The same goes for kill pots in kill games, people do not up the aggression to try to win the pot early, and profit on the temporarily raised stakes.

If a lot of people are straddling I'll do it because I want to keep the action going.

There is a neat trick I saw once. Get a straddle amount and tie it together with a rubber band. Explain to people that whoever wins the next pot from you gets this bundle but should use it to straddle when it's their turn - and whoever wins that pot will get the bundle and should do the same. Sometimes it gets a lot of straddles going, sometimes not.