It's 50 minutes from Capital Hill to Green Lake. Over an hour when you factor walking to the stop and waiting for the bus. That's over two hours round trip. Makes getting together for board games or dinner a huge pain in the ass.
Getting to Kirkland is 90 minutes one way. People and jobs are scattered all over the greater Seattle area. The vast majority of people I know have cars. The few who don't are rarely seen outside of their tiny bubble because it takes so long to get around.
Other than that... I'm really at a loss, I don't know what I can say. Again, this isn't a problem with living carless or even living carless in Seattle, it's a problem with your special case with your specific social group. If your bubble induces you to make a 25 mile round trip to Kirkland with any regularity, yeah, you should probably find a way of getting there that doesn't involve bumming rides all the time. But everyone lives in a bubble, there's different kinds, sizes, and geographical dispersion levels of bubbles, and there's nothing wrong with living in a geographically concentrated one. Capitol Hill gets you to either U District or Lower Queen Anne with an easy 20 minutes transfer-less bus trip, it's 15 minutes to Belltown, and so on - it's really far from a teeny tiny bubble. (Not to claim Cap Hill as centre of the universe, I'm merely using it as an example I'm familiar with, not living in Seattle.) You don't need a car unless your social group dictates that you do.
Hiking, snowboarding, sure, that requires going out of town. (Zipcar or rent.) Staying in town doesn't need a car. (And try parking in Capitol Hill and let me know about preferable.)