Street cycling - even with bike lanes - can be terrifying, especially for those without experience. In the urban environment cars, trucks, other bicyclists, pedestrians... all operate in a very unpredictable way that frequently forces you to make snap decisions that impact your safety directly. It's chaos, and it's very intimidating.
Even if the weather cooperates and the distance is reasonable. If it is dark and raining it feels miserable and dangerous.
I totally agree that when I can bicycle to work, I arrive in a much better mood, assuming I didn't almost get killed or miss my transit connection. Commuting by motor vehicle (in my case, mostly motorcycle) builds frustration and stress. But the bicycle takes 45 minutes more each way, and the return commute - which is almost all uphill and in the dark - is just impractical in the winter.
I'd advocate we give up on the "huge suburban campus" model of offices that assumes everyone will arrive by motor vehicle that takes the freeway, and build more offices near residences, but I don't know if that kind of thing will ever happen.