The big ticket items could not prosper without the use of talented companies/individuals who can properly represent them though.
I mean, who is really going to spend upwards of 5K on a component mail order? Maybe a few, but I think the majority of clients who want that type of item want to see, hear, touch and feel and learn what it is capable of from a knowledgable person who can demonstrate properly.
If I have the choice, of auditioning an item directly from the manufacturer with an in home trial (say 30days in my nicely fine-tuned system) vs. going to a dealer who has the item sitting around and may demo it on different equipment in badly set-up rooms and offers you only a few hours time - not much of a choice - I would rather go manufacturer direct. There could be traveling demo models that are shipped from place to place to allow people auditioning for free.
Also talking to the manufacturer directly you get quite often more reliable and accurate information than from many dealers.
As for the marketing - Do dealers and distributors really do so much marketing that the manufacturer couldn't take over that part?
There are some rare exception where dealers can make a difference and that do provide excellent service, but sadly those are in the minority these days. In the other cases, I would rather deal with Nelson himself than the Pass dealer in town who doesn't have most pieces in stock and won't allow you to audition the pieces at home either.