It doesn't have to be a lifestyle choice. I bike every day, except when my bike is being serviced. I always dress for the destination, and that's what virtually everyone else in this city does.
Yes, my way is what old timers do (I have been urban cycling for 30 years) but we are a tiny minority and the rest of the commuters just use whatever clothes are their daily standard, with maybe a slight adaptation... Still I don't understand how they are comfortable in any but mild weather conditions: specialized cycling clothing is so much more comfortable in heat, storms, snow and anything in-between - and I most people in the office have no idea I commute by bicycle (though they may suspect it when they contemplate my gorgeous ass)...