Strengthens your immune system. Without exposure (playing in mud, touching other people), we are only weaker.

Bio life is really complicated.

Sterilization works well only to a certain degree, before becoming damaging, e.g. causing resistance.

Somewhat related, here is an interesting visualization of bacteria developing resistance to antibiotics.

https://www.youtube.com/watch?v=plVk4NVIUh8

Its shocking really. But the bigger problem is how do you know what germs you are exposed to? Germs are everywhere

....10x worse, gas pump handle.