Full time other than work, which sort of answers one question right there.

Is it a lifestyle choice? Sure, in the same way that eating vegetables with every meal is a lifestyle choice. It's something I choose to do, but I do so because I like the comfort, the style, and the historical connection (even with modern kilts)

Did I give up any hobbies that require pants? Well I never had any hobbies that required pants. I've done some things in a kilt that others thought crazy (skiing, snowboarding, paintball) but to be honest my biggest hobby REQUIRES kilts (Highland Games).
If I need to wear pants, I wear pants. It's a non-issue.

Do I do it for the attention? I honestly don't notice much attention. I get some, and some of that I would just as happily do without as I generally don't like talking to people if I have the choice. Sometimes though the kilt has opened doors or been an icebreaker that led to meeting some nice people and having some wonderful conversations.