Those at the highest risk are free to wear KN/N95 masks to protect themselves.
The problem is that while N95 and P100 masks offer better protection in the lab, in practice they only have about a 40% efficacy in preventing infection. https://uwaterloo.ca/news/media/study-supports-widespread-use-better-masks-curb-covid-19
This is among trained professionals though, and the efficacy drops to zero when forced upon toddlers and children.
The linked study (and others) shows it's better to focus on better indoor air quality in general - which was already a problem long before COVID.