I am mostly a shopper, and have to say I agree. I do use MP as the quickest way to find items, but will more often than not look for an in-world store. I do have a hard time understanding why so few merchants add the fees onto the MP price, or is that something already experimented with? Getting around those fees is a great motivator for me, and it feels like a reward for shopping inworld. In the past, I have also turned up inworld to check out an item and seen so much more, or just enjoyed the ambience so much that I go on a spree, something much rarer just looking at a page of listings.
I will say that MP listings can carry a lot more product info than you get inworld, so there are times I'll be standing in a store checking out the MP, and on occasion I even bought the item from MP as it was cheaper there! I know, doesn't really make sense but hey. I do hope your post sets something rolling, inworld is the place to be