Yes, I wonder about that. I picked up some of these:
and they include an enormous expanse of filter. And even so, their descriptive material says they chose to go with an n90 filter instead of n95 so it’s easier to breath. Admittedly, this was originally designed for exercising in polluted air, and the company pivoted to “virus protection” when it became obvious that would be a large market. A mask for grocery shopping or waiting to see the doctor doesn’t need to be as breathable as a mask for running. But still – even with that huge filter, they worried about breathability.
(This mask is easy to breath through, by the way, but I don’t find the hard plastic frame very comfortable, as it’s designed for someone with a flatter nose. It seals well, due to the silicone, but the bridge of my nose gets sore if I wear it for very long.)