Vendors will often supply lender gear in some cases, or provide a loaner. All of which is not instant for the customer, but then, it's part of that service.
I think this is part of the problem, but not all of it. But for whatever it's worth, everything you see at a brick and mortar is bought and paid for. No loaners. It isn't cost-effective for the vendor -- how many loaners would they have to have out? How many dealers could they support? Apparently, this isn't viable.
Magnepan is working on an alternative, dealer mediated, direct-from-the-vendor in-home money-back trials. It's interesting, but still, doesn't keep the dealer from having to maintain and invest in demo inventory -- but perhaps it'll eliminate the requirement for dealers to maintain so many current models on the floor.
I think the answer is stricter controls, unfortunately. Unless the vendor wants to go direct -- which will limit it's ability to scale, provide good service, or keep costs down -- they need their reseller channel to thrive. Which means they're going to have to crack down on "bad" dealers, limit internet sales, prohibit discounting, and the like. The dealer can then make a profit, stay in business, and off-load much of the support, maintenance, shipping, overhead and customer relations costs from the vendor.
The problem seems to be guys that discount, honestly. They gut the market. The vendors need to wean themselves off these guys -- but since they've already "gone there" and enjoyed whatever volume these guys have been able to move (and the fact that they're the only ones moving things in times of economic distress), isolating themselves from this income stream will mean starving -- until the reseller channel can rebuild and get healthy again, which would mean (hopefully) even more volume than before.
The challenge is surviving the gap. Everyone in the chain needs revenue to live and stay in business ... and how do you tell a vendor to tighten their belt "for the good of the industry" when their competitor isn't doing it? In fact, if that competitor is smart, they use their advantage of a continuous (if deflated) revenue stream to build market share through advertising, innovation/investment, and/or acquisitions. Which, obviously, only compounds and perpetuates the problems ....