I've never even considered them. I doubt if any of them are constructed in a way that doesn't affect photo quality. They aren't made to the same standards as filters for camera lenses.
Far from the standards for good camera protectors/filters. I normally paid, on average, over $150, for just a protective (UV/Skylight, 1A/1B) type filter, all were coated to prevent flare and won't even note costs for specific filters such as ND, POL, etc. And only filters from Hoya B+W are used.
These so-called protective filters are nothing other than plain glass.
Will they offer some protection, probably. However, looking at the teardown of the phones by the guy with the razor blade, he goes after lenses with that blade an no damage is done.
I prefer to case that keeps the lens away from damage. Something that keeps the lens about 1-2mm away from a table top.
My pixel 4XL has no scratches on the factory camera lens and has been in/out of my rear pocket, laid on a table more times than I can even count. And NO scratches.
However, to look at this subject honestly, people usually do not take their phone photos to blow up to 12x18 to sell and/or hang on a wall; the vast majority are sent via message, email, facebook, etc. to friends for their viewing or friends and relative are made to sit through a showing of a person's vacation/Kids/grandkids photos and movies using a cast feature to the TV. (Similar to the 60s/70s slide/8mm showings where people could not wait to run out the door screaming to the nearest bar.) So a cheap lens cover will not cause any problems other than adding possible flare.
And if people do not note a problem with their photos/movies while using lens covers; that's all that counts.