If you never get another bloke's bum chocolate on your hands you never build up immunity, in the same way that kids don't play in the dirt like they used to, so are arguably more prone to picking up infections and developing intolerances. If you stopped and thought about it too much you'd never touch anything - there are more than likely traces of shit on just about every handle you touch, not just toilet door handles, toilet flush handles and tap heads.
Which is why we have something called "faecal transplant" - google it......