I've read that bowl-coatings are a means of keeping pipe buyers from burning out the bowls from over-smoking and starting burned patches. From my experience, this would be a rarity, but maybe it was a problem when the pipe industry was larger, and to volume pipe makers today.
This.
Yes, but almost all burnout is partially user error. Or, rather, almost all burnout involves some user error. In my unscientific estimation, about 10% of burnout is because of very serious unforeseen and unseeable problems in the wood. 70% is a combination of minor faults in the wood (which are just a thing; it's briar, not steel) and minor user error (ranging from minor stupidity to the sort that, on a bad day, any of us might commit). The remaining 20% are the function of real user idiocy.
In reality, manufacturers take all, or almost all, of these back because that's the way it is. Short of someone saying, "well, I was smoking it while in a wind tunnel testing jet engines while using a trip torch lighter," it's just all a huge gray area. So, as an industry, we just make good on these.
Bowl coating, either as a matter of company or maker policy, or selectively, seriously cuts down on burnout rates in the first few smokes. Unlike, say, consumer electronics where most of the cost is in design and software, most of the cost in pipes are hard costs: factory labor, briar etc. Moving burnout rates from 2% to 0.5% might be the difference between a factory making money and not, and it certainly helps to hold pipe prices down a bit for factory pipes.
I have to say that I wince a bit when I hear people remove bowl coatings. I caution against it because it's not fair to go back to the manufacturer if you do have a problem if you've altered it before smoking it. Take out the bowl coating if you wish, but it does reasonably limit your recourse for replacement.
Sykes