Does a car salesman add value? Do you believe what he says about the cars he sells compared to other cars? Get real.
Honestly, there are a few, very few. Some carry stuff they believe in. In southern Cal, I can think of Gene Rubin, Brooks Berdan, Randy at Optimal Enchantment. Some are retailers who try to carry good stuff at price points and offer helpful advice. Try the people at Reference Audio Video, mail order and internet, but you can talk to them on the phone, and if you are in southern Cal you can go there and listen to stuff.
In the UK, Alastair Gardner, at signals.demon.co.uk or something like that, is welcome to stay at my house anytime he comes to southern Cal.
And then there was, let's see, starts with L, what should I call him, I'll make up a name, Lloyd. I knew Lloyd when he was first in the business, worked the scope to set up cartridges, did maintenance and sort of acted as a salesman. Answered questions honestly. Unfortunately, he was too honest. Lost a lot of sales. Saw him many years later working in another store when I was listening to a very nice EAD cd player. Knowing my values he recommended something his store didnt carry, a meridian 506, which I subsequently bought from someone else and still have in my second system.
Mel Murakami (Audio Haven - defunct) was another. Would answer questions and take time over the phone. He had two problems. One was location, the other was when you talked to him on the phone and suggested you might drop by he always said to call first so he could warm up whatever you wanted to listen to. Sort of discouraged impulse shopping.
So, the answer is some do, most don't. But, if you decide to buy something because you liked the way it sounded in a store, for goodness' sake, buy it from that store, even if it means paying a little more than you would on the internet. They provide a service in making stuff available to audition, and if we dont buy anything from them, they'll go away.