It's another useful thing the phone can do and its also a bit cool and exciting making purchases with it for now. The added security just makes it a no brainier to take advantage of.
Speed and security. I am very excited for the upcoming time where I can feel confident in not carrying a wallet for payment options, and not have to worry about ever having my card numbers stolen.
I picked the first option, but not cause I feel like the cool kid. More just cause it's a new toy (I have no delusions that it's "cool" though, but it is neat). That and I do like that it is a lot more secure.