I really don't see it as the retailers responsibility to set up new instruments.
Almost all other instruments are shipped from the manufacturers in their best playable condition.
Pianos are tuned and regulated. Saxophones are checked for leaky pads and spring tension is adjusted.
The whole issue of bass guitars being poorly set up is not universal.
There are many bass builders who take enough pride in their products to make sure that they are set up and playable before they leave the shop. Some obviously do not.
High volume manufacturers may likely have QC process by which they isolate instruments that are less than good and send them to big box retailers thinking that they can slide them through and likely not see them again where as smaller retailers may send them back in exchange for better stock inventory.
Those less than perfect instruments that get returned to the manufacturer are then re-packaged (maybe) and shipped off to a big box retailer where they are taken out of the box and hung on the wall.
The good ones sell, the bad ones stay on the wall. Before long as this happens a larger and larger percentage of the instruments on the wall are the duds. Then you end up with a mega store that has mostly crap and the store gets blamed.
Great observations. This explains why I am usually more inclined to buy a bass long-distance NIB (with the option to ship it back no-charge or return to the store if it has a major flaw) or gently used from a seller who will answer all my questions and give me reasonable assurances it's a winner. In truth, I rarely buy from brick and mortar stores, for some of the reasons you outlined. We have Wildwood Guitars and Drum City Guitarland near my home base, and those folks go the extra mile with things like inspections and set ups, but many stores, even small mom and pop places, aren't putting in the effort.
We here in the USA used to live in a customer-service oriented retail society. Those days are all but gone. In general, we don't consider each others' needs very well these days. I can't remember the last time a young person said "Thank you" at the drive-through window, but it's pretty rare. It's just not taught or expected.
So it is with retail. Instead of service before the sale, it's now all about service after the sale; warranties, returns, etc. More and more, the consumer has to educate himself and understand the product even better than the sales staff. Sad but true.
Now, with something like a dishwasher, that's a big learning curve and a pain in the butt. I don't want to be a dishwasher expert or repairman, I just want clean dishes.
But with my musical instruments, I somehow don't mind so much. I do want to be an expert with my instruments, as smart or smarter than the sales staff, so if I've been forced by the social retail dynamic to learn how to "rescue" a neglected bass with a few simple hand tools and a 20-minute set up, that's only going to make me a better musician in the end.