https://www.mcmaster.com/respirators/half-face-respirators/
Again, they MUST be donned correctly and OSHA REQUIRES a medical exam PRIOR to use in the business sector. You MUST complete training and a fit test annually as well. They are NOT meant for "airbourne diseases". What you are filtering matters.
So, to his point they do exist. But so does bunker gear and level A hazmat suits.
To your point, they are not meant for the general public just because you can buy them. It is extremely dangerous to use them if not worn correctly, trained or have a medical evaluation allowing the use.
I prefer cotton mask in public because I can wash them and it is enough for what I am doing in public. Other wise I use the required type at work for the hazards I am working with per OSHA.
When making sammiches I use a quality food grade.
When I am on a face... Wait wrong thread.