Well, you do shoot in environments where the extra protection is needed. Some people actually live in such environments (good reason for getting a waterproof case or gear insurance, which may be much more reasonable investment than filters). However, many people, don't. So my statement stands.
I agree about the cleaning, because we just don't care that much about filters and what we clean them with. I remember using my Sigma 150Macro for two weeks every day and I didn't bother putting the lens cap on. No filters were attached, I just kept the hood on and the front element stayed pretty clean all the time. Actually, I don't remember it getting dirty (so it would require to clean it immediately) at all. That hood is a deep one, so this trick may not work that well for UWA. Outdoors, I only used a microcloth to clean off some fingerprints from my hoodless primes (ohh greedy canon ) after someone grabs the camera to see pictures and they come off easily (if the cloth is clean of course). You just need to wash the cloth from time to time.
There are professionals who not only use filters instead of caps, they generally don't care much about keeping those filter clean + they never use hoods and shoot JPG . Like you said, it just works for them. For me, I'd get an extra lens rather than putting a filter on each one of them. Everything is subjective. UV filter has no effect on pictures until it does and it is OK if you can ignore those rare occasions. I mean it may noticeably affect pictures in some specific circumstances, not all the time (and not in filter promoting lab test results ). It happens, please stop denying that.
I think we are both saying the same thing- it is subjective, and differs from case to case.
I said in MY case it doesn't significantly affect the IQ.
I am sure there are people whose pictures do get affected. And it totally makes sense for them to not use filters themselves, or at least not all the time.However, preaching everyone else not to use it is a bit presumptuous.
Again, in MY case there isn't usually a concern about mud, water, etc. to a huge degree. But then again- few days back I was on the Maid of the Mist, shooting with my 24-70II inside the Optech Rainsleeve (which is great for protecting your camera but not your lens, by the way). I was feeling a lot better with a filter in front even though the 24-70 is water-resistant.
People obsess over little things and start these long discussions, and that is fine until it isn't and there are personal attacks and insults. You mention washing your microfiber cloth- you should see a thread that discusses whether or not you should wash it with regular laundry