“Didn’t they wear those surgical masks for their own protection?”
Yes. As mentioned surgical masks do provide some protection to the wearer.
to illustrate (these numbers are not at all accurate just to illustrate a point) Say a mask reduces your odds of catching covid-19 by 25% . If you are seeing many patients with covid 19 (Ie healthcare workers) and your odds of catching this contagious disease with no protection is 100% (for illustrative purposes) then reducing it to 75% is significant.
If you are not a healthcare worker and are not in contact with anyone who has covid19 and are going about the community where your odds of getting it are 10% reducing that to 7.5% is not that significant.
Again just for illustrative purposes, I made up these numbers .