in my opinion, there are several "common beliefs" in respect to guitars that I totally or partially disagree with.
firstly, I am a woodworker by trade with near 20 years finishing wood furniture with various products, and have a pretty decent understanding of wood finishing - which of course all guitars are.. wood.
I think a more modern finish, be it a polyurethane, a conversion varnish, catalysed lacquer, etc are just as capable of providing as thin a coating as "nitrocellulose lacquer", its just that since you can spray a lot more on and build up a thicker finish, many do. The advantages of a thin finish is the same no matter what that finish it. Likewise, a thick finish (whatever it is) is detrimental to the sound.
You just cant beat a good, modern product for durability, and unless you really like the softer finish that NC gives, and the fact it will check over time, I cant see it adding anything.
I personally use a two part catalysed lacquer. I apply it thin as I can with still filling the grain. It is a clear, tough finish that can be built up in multiple coats in a day, and rubbed out within days. But it looks like NC, other than it wont check even when going through many cold warm cycles.
One other thing... that bit about wood breathing better through a checked finish is false. Any decently applied wood finish will still allow the wood to undergo seasonal changes in moisture content (what breathing is). Unless you are talking a thick, polyester finish or an extremely thick finish of anything - the wood will breath just fine without checks. Trust me.. wood moves and you dont stop it with a few coats of finish.
I will never use NC lacquer myself, because you can use an as thin coating of something so much better these days.
Lastly, NC lacquer is considered the EASIEST finish to apply in the woodworking industry. No mixing, no fancy recipies... just open the can and spray, the only thing I can see harder is that fact each coat softens the one underneathe and a burst finish can sometimes be ruined with a sag if you get too heavy with the gun.
I like talking about wood and finishes...
Again, these are my own opinions with my personal experience. Nothing more.
AJC