I have a similar problem, but I don't think lack of lip reading is the problem for me. I think a lot of people simply mumble when they have a mask on. Something about the sensation of the mask on their face has them start slurring words and speaking softly.
For a large segment of the population, the act of covering the mouth (regardless of whether it's with a mask, a hand, or something else) activates a deep-seated submission reflex.
Different individuals submit to varying degrees, and in different ways.
Some people become very quiet and withdrawn, which can lead to the problems you describe when they try to communicate verbally while masked.
Others feel intense paranoia, and desperately seek out authority figures to latch onto.
Yet others realize that they're submitting, and it makes them feel weak and powerless. These are the individuals who often react aggressively when encountering somebody who isn't submitting like they are.
Sure there's an element of that, but for some people it seems much worse than others. Some people can still speak clearly with a mask on, but many people can't.
It can be particularly bad when there is a plastic barrier of some sort in front of the masked speaker.
Even today, this is still pretty common at cashiers and checkouts in Canada, for example.
Many of these barriers were put up rapidly without much thought, and are completely improvised. They aren't like the purpose-build security shields that still have holes, vents, or microphones/speakers to allow at least some verbal communication to take place.
The thick, rigid plastic barriers are the worst offenders, by far, although even flexible plastic sheets can definitely disrupt communication, too.
