you're right bout needing new shorts every day, but saying that it's usually not done.
The actuality of touring means you can only carry so much and the day to day means that laundry is probably not every night.
Touring last year through Cali/ Oregon i packed light with 2 shorts and planned on hand washing every night. Of course nothing dries there so hand laundry was impossible. So the number of shorts is the number of days between launrymats. If that days ride dosn't pass a laundrymat...
baby wipes.
every night change clothes, wipe your...um self... and then the chamois.
same rules for very very long tours where you don't have a change of clothes.
Keep the body clean, keep the chamois clean.