Joel's experience working for Microsoft shaped his mind. It has been MS trademark to start slow but building a _SURE_ thing with good architecture (security is a different story).

How old is MS Office now?

Compare that with Silicon Valley startup mentality: code like crazy, take shortcuts, release early, flipped your company and let the new hires figured out the mess.

(Or you could opt for re-writes like the Reddit people have been doing since their inception).