I commute without use of a car. It would be totally impossible for me to do that without using a lock...and I'm not going to use some POS just because I'm worried someone might steal it. That's why God made insurance (or the Danes). My gym would never let me store a bike there. My office building is a 55 story monstrosity...think they let bikes in elevators? It's safe there...in an underground parking lot, but still needs a lock. The local grocery does not let you walk through with a bike. Bars don't let you store a bike inside.

Your motorcycle analogy is off IMO...they're worth far more on average and I see locked ones stay for years in my Philly area. I think they have more sophisticated thieves than the average bike thief. Most bike thefts in this area are one of two things:

Crack head who gets lucky and sells it for $50.
Roomate/neighbor who steals it from a communal area.

You lost a bike to a chain cable that can be cut with a hedge clippers...I dare you to get through a NY'r in 45 minutes. Are there expensive and sophisticated tools that can do it? Sure...the people stealing bikes aren't really the ones with those tools.