I'm pushing 40 and have never owned a car. For me the bike has always been my main mode of transportation. I didn't start out to be an bicycle evangelist but just kind of grew into the role. I see the bike as a tool to change the world. It doesn't pollute, it reduces traffic congestion, it's cheap and it's good for you.
As a kid riding my bike was freedom and I guess it still is. On a bike I'm not constrained by long line ups of traffic. No matter how busy the roads are I've never experience stop and go in the bike lane. On a bike you can take short cuts through the park or a trail that isn't open to cars. When I talk to people about commuting by bike they say the car is faster. Depending on where you are riding, this may be true but time in a car is not productive. If you are riding in a city core you will often be faster on a bike plus you don't have to find a place to park. Every street is littered with options to lock up your bike.
When you ride instead of drive you get to know you town a lot better. Exploring back streets and bike only routes lets you learn the inner character of a place you never get to know in a car. And on a bike you see so much more. I've found little mom and pop restaurants on my trips that I didn't even know existed. When you stick to the main drags there is so much you will never know about.
If you are a two car family you can save around $5000 per year by ditching one car. The cost of the car, gas, insurance and maintenance really adds up. With a bike you have to lube your chain and get a tune every now and again but the costs are so much lower that one year of commuting will pay for a nice vacation.
When I'm on my bike I'm happy even if it takes a few minutes more. When I'm too busy to workout, I get a couple doses of exercise every day with the ride to and from work.