Question about San Francisco mint marks

This question started with my own personal experience collecting Morgan’s and I thought I’d ask it. But a recent discussion with my son has me kinda digging deeper. I am relatively new to collecting. It started with a few Morgan’s I received about a year ago and the with the sudden run on silver I noted more and more popping up in the melt bin of a gold/silver place by my work. I felt it was a good thing to rescue some history if I could obtain them for reasonably close to spot. But in doing so, I have noticed a large lack of “S” mint marks on any of the coins in this area. Predominately referred to as the Midwest ,but many dispute Ohio being in the Midwest. (I will just say it’s Ohio). Tons of “P” and “O” mint marks but rarely can I find “S” mint marks. Even at the few coin shows or antique dealers. I have found myself noting mint marks and RARELY do I see an “S”.

Congruent with my Morgan collecting my son has gotten into penny’s. We find the same problem, rarely do we even see an “s” mint marked coin.

I thought I would ask, is this due to logistics of getting to Ohio when Denver (pennys) and Philadelphia mints are closer? Or is it purely because of the numbers being produced in the San Francisco mint? Or because people hoard the “s” mint marks?

My son and I were discussing it last night and honestly I just want to give him the real answer. But I said I’d ask the question. Thanks!