It is easy to see who's never worked in a music store, or who has never been on the hook for inventory.
A couple of points from someone who has been on both sides of the counter for a lot years. First off - the instruments on the wall are not "demo" instruments unless you're talking very low end stuff. For instance, if you play the cheapest bass in the store and say, "I want one" they may (*may*) go to the back and bring out the new triangular box for you. Or you might take home the one you played. I recently bought a lower-end Goodtime banjo package for my son and that was the case - there was a demo that could be played and if you wanted one they'd go get you a new one in a box. Which they did. And I pulled that one out to play it first to make sure it was as good or better than the "demo."
But for anything beyond that the bass on the wall is there to be sold, not to exist as a "demo." Yes, you can generally play it. And back in the day I remember going to GC and playing half a dozen strats (some being brought from the back) to try and find a good one. Of course I was respectful of the gear and the salesguy's time, and was serious about buying one...and I did (actually the 13th one I tried). You don't have a dedicated "demo" model unless you're moving a lot of product.
No way I'd play one off the wall, like it, then ask for a "new one" from the back and not play that one as well. And if the first one (the "demo" one) was better, I'd take that one.
Cars/motorcycles are somewhat similar. At most car dealers you can drive *any* car on the lot if you're serious. They may have a demo car, or they might not. Actually in my experience motorcycle dealers are more likely to have a demo model that they then sell after some number of miles (determined by the manufacturer and then priced accordingly). I've been to car dealerships that didn't have a specified demo of each model. Whatever was on the lot was fair game. But it is up to the salesperson to figure out how they want to apply the "rules."
