Aggressive know it all salesman

Why is it that of all the things I have ever bought - fast cars, nice watches, nice clothese, good food - it is the audio salesman that is the snootiest know it all snob of the lot.
I don't adertise my knowledge of audio, which whilst not encyclopeadic, is not that of an idiot either. I recall calling up one supplier to just ask about a pulley for a turntable, and before you know it I got lectured about why DC motors are better than AC. I ended it saying that: I have an ongoing project; a very good battery powered DC turntable as well; two superb DC direct drives, and an idler drive project on the go.
This isn't something to level at all people in audio, I found the guys from Absolute Sounds i nthe UK very approachable and enthusiastic - they weren't the 'audio snobs' I either feared or expected. Likewise it is lamentable that Les Wongs Walrus Systems is now defunct. But we all know the dealers and suppliers out there that are such idiots - bit like the 'haughty' french waiters of yesteryear.
When I want to buy something specific, or if I was just enquiring I really do not expect, nor appreciate being spoken to like an idiot or a child, nor do I think it helps the industry when the people in sales think that you almost hae to be part of a kind of 'in the know club'.
I would appreciate your thoughts on this