I ride (did until I had spinal surgery, but will again) to and from work. I've had 60 mile commutes, 3 miles, 12 miles (about right!!) and currently have about 30 miles, which is O.K. Why do I ride to and from work?
1. Time: Even the 35 miles each way to and from Birmingham was faster or about the same in terms of time on my bike riding in at 6.30 am. However, getting home was a different matter, I could be home in 1.10 on my bike, in fact, wind assistance or misery accounted for I could be very accurate with my arrival home on the bike. Riding at a fairly brisk pace.
My record sat in my car on the M42/M6 was three hours and fifty minutes to cover 35 miles. I never took this long on my bike but on the other hand could not listen to Radio 4. He giveth and he taketh away.
2. Training: I have a life outside of racing/riding. My wife is very patient but I would not envisage her being too jolly if I topped up my 45 hour work week with the 10-15 hours riding time afforded to me by commuting. The option to throw in some intervals, hill reps, tempo and threshold work is handy. Ragging the mountain bike cross country in the winter is good for skills work and good fun. Why don't we get so cold on mountain bikes? Wind I suppose.
A sweet recovery ride in the morning sun is a fairly nice way to start a day. A thrash through the traffic into rolling hills is a nice way to end it.
3: Money: In the UK petrol seems to occupy the mantle of 'luxury goods' alongside of Rolex watches and those massive headphones I see people rocking out in. Porridge is cheaper than petrol, and porridge is my fuel. I do own a car but it's crap and rarely moves.
4: Fun: Depending on your disposition, riding in cities is fun. It firms the nerves and skills, hones the senses and only slightly destroys your lungs. Thankfully not as much as car drivers due to the air intake/exhaust relationship.
5: Smugness: Not really! I actively resist the 'smug rider' clan. Cars do not emit much crap any more. Significantly less that cattle, energy production, air travel etc etc.. Bicycles are mass produced and often made of alloy. Carbon production is horrid and the side effects for the Chinese workers are nasty. Tyres are made of rubber, rubber production is not the most friendly process. I ride because I enjoy it and it is convenient. If you enjoy the rattle of the train, the comfort of a Mercedes S Class or the John Travolta like rhythm of a funky walk then more power to you.
Whatever you ride, however you ride it; enjoy it.
PS - Left ear for podcasts (usually cyling360) right ear for traffic is O.K. But a duo of ear plugs for Metallica is not clever. Lose the buds kids.