Honestly, the most important padding is in your bum muscles. Don't ride much? Your bum will hurt. Ride to work every day? You'll be fine. Padded shorts improve both situations.

You definitely have to wash your shorts every day, for the same reason you must vacuum and dust your entire house every day. Some of us are substantially less diligent, with no ill effects - though more than 5 days between washes is getting a bit much.