Exposing everyone to the same ~25 cases is almost certainly noise levels compared to the diversity of things you'd find just from checking an adult human hand t

Exposing everyone to the same ~25 cases is almost certainly noise levels compared to the diversity of things you'd find just from checking an adult human hand that hasn't been violently purged with antibacterial agents in the last 30 minutes. Also, IIRC many of those aren't live viruses, so the fact that they grant learned immunity to a handful of highly risky diseases is not necessarily relevant to how helpful they are in training your immune system's friend-or-foe responses on a wide variety of inputs.