I can't speak for other trades, but I have enough experience doing carpentry (mostly on the side, but paid) to say that Home Depot/Lowes/Local equivalent building supply stores are where carpenters and general contractors buy their tools, or at least that we're buying the same models that are available at Home Depot regardless of source.
Interesting. In my limited experience with pneumatic tools, SnapOn is much higher quality than the brands available at big box stores. Probably not worth it for typical homeowners, but my old roommate ran a SnapOn truck.
My dad's company was hired to do work inside a facility that made sockets. At the end of the line where the sockets were being prepared for packaging, the sockets would get separated and sent down various lines where they were stamped with brand info like Craftsmen, SnapOn, Husky, etc. They were all the exact same socket. It's not like they ones that passed a 16 point QA went to SnapOn, the ones that only passed 12/16 points were stamped Craftsman, and the ones with lesser scores stamped Husky. They were all identical.
If the sockets were this way, I would also expect that to be the same across the things like wrenches as well. The great thing about SnapOn is that truck. They will show up without the need for you to go somewhere. Their warranty wasn't any different than Craftsman's life time warranty, except you had to find a Sears.
I recently had the opportunity to take apart somebody else's MAC battery-operated impact wrench, and found it was exactly the same as the DeWalt one on my bench. It's just molded in red plastic instead of yellow. The advertised torque rating is slightly higher than the DeWalt, so maybe there's a subtle component difference in the (epoxy-potted) motor control module. I hope the guy didn't pay too much extra for it though.
Anecdotally, I use my Harbor Freight (non-impact) sockets on my impact gun. I've never broken one. I've broken tons of Craftsman sockets with far less force.
I have never once in my life seen SnapOn tools on a job sight.
Kind of beside the point, but you don't really even see pneumatics in construction much anymore. The _only_ pneumatic tool on my current project is my framing nailer. Every single other power tool is electric (mostly battery). Some companies are even making battery powered framing nailers now, and my corded worm drive saw finally broke after 15 years so I think I'll be upgrading to a battery powered saw in the near future. In a few years, I expect I'll be able to frame a house with entirely battery powered tools.
SnapOn is famously desirable and expensive. I think part of this is that there are very few truly "premium" construction tools because, well, they are used in construction. Your drills and saws and the like are expected to get beat up and may need replacing. You may need more tools if you get more workers one day and fewer tools the next. Obviously there is still a range in quality and I'm sure we've all noticed the difference between a good name brand tool and a more budget option, but I think the ceiling is intentionally kinda low.
Small construction tools (drills, portable table saws, angle grinders) is largely done at big box stores, however smaller stores sell a fair amount, plus specialty product, but the bread and butter small tools are big box stores. Quality is the same, and prices are generally lower.
Shop equipment used to be done by trade show, not sure how it works these days.
