You will have plenty of exposure to microbes simply by existing outside of a sealed sterile chamber, and microbes != pathogens. There's no need to encourage exposure to and infection by pathogens, and this idea often results in increased risk or severity of disease. See: "chickenpox party" intentional exposure of children to varicella, putting them at risk of shingles as adults, with the risk increasing the younger they are at the time of infection.

https://en.wikipedia.org/wiki/Hygiene_hypothesis?useskin=vec...