They are great too, but if you live in a high bike crime area, you don't want to deal with super locking your bike at your destination. Dealing with stolen tires , seats and handlebars is aggravating as hell after the 3rd time.

Also bring your bike on the train, and then going the last 2 miles to your actual destination is pretty annoying too. It's much nicer to just grab a bike at the station and then leave it at work.