I feel like this thread's title is wrong.
"I personally can't think of a good reason to get married" Would be more appropriate.
There's people that see a good reason to marry, and who are you to tell them there are none? If you don't want to, that's fine. But if there are people that feel there's a reason, be it love, lower taxes or w/e. YOU decide whether or not you think you have a good reason. And if you do, go for it.