Consider that bacteria are not the only things you could pick up. There's plenty of other parasites to choose from.

There is a reason we ask people to wash their hands.

You're immune system is probably not going to improve on exposure to worm eggs or larvae for example.

To take it to an absurd extreme, if you come across an unflushed public toilet you're not going to drink from it with the hope of boosting your immune system... are you?

And to take it to the other absurd extreme, you’re not going to throw away all foods that aren’t kept in a sterile vacuum until the moment it’s consumed… are you?

I’m arguing against being overly-concerned with hygiene to the point that you cannot even handle touching everyday objects without a significant disgust factor. You’re talking about licking toilets. Come on bro.