I am a believer in protective filters. Yes, modern coatings are very very resilient. But a little extra protection doesn't hurt. I have lost protective filter a few times in places, (Africa as one example), where the nearest front element repair shoppe was days away. I was able to carefully remove the filter and keep on shooting. Additionally, some lenses are not weather resistant unless a filter is in place. One of the things you pay for is coatings, when you buy a filter. Typically, the more expensive the more coatings. The more coatings, the less flare/ghosting you'll see.
Most filters from a quality filter manufacturer won't/won't significantly degrade the image. The main problem is flare. A protective filter increases the propensity and the amount of flare. Coatings go a long way to reduce said flare/ghosting.
One of the problems with dust is cleaning the dust off. Over time, the tiny abrasive particles found in dust will eventually and minutely scratch and destroy/remove/harm the coating. For me, it is easier to replace a filter than a front element. (This probably won't happen on a single trip to Africa ... but over time...)
That's just my opinion, I am sure there are many who think to the contrary.
PS- I also believe in Murphy. For me, the moment I walk around sans filter, is the moment when a dust storm, some acid, small piece of shrapnel, Sharknado, et al all hits the front element.