Like others here, my perspective is my observation of Guitar Center.
Though I think there is a valid point with regard to knowledge of the staff and that is very much true, for me it was inventory. I'm usually pretty sure what I need to know before I go. I mean, I have purchased two guitars from GC locations (my Taylor acoustic and my Gibson Les Paul...which was on a really deep sale price).
While I do get that you can't be all things to all people, I find that most GC locations I've been to are just underwhelming. When you walk in the door, you see the $149 beginner package. Even though most folks walking in the door won't be buying a $2000 Les Paul, there is something aspirational with guitars. We all have different aspirations but GC sells guitars but the do poorly selling the dream.
Though I don't know the financial postion of Chicago Music Exchange (CME), that place totally sells the dream. If ever you're in Chicago on the north side, go there. No matter your vibe for guitars, you'll walk around with your mouth dragging. The picture below of me is a Gibson Les Paul goldtop that was one of the models on floor stands at CME (most guitars are wall hung). You can just grab and play an amazing guitar. GC? They have two Gibson Les Paul's and they are a mile high behind a counter. You feel like you need to know the secret handshake.
GC does not sell the 'wow' of guitars. I know to some people, that's not a big deal. Much the same way people look at a Mecedes and think all that extra cost is a waste. It's a very valid point.
No matter what you enjoy, most people want to attain the dream of whatever it is.
Guitar Center is selling not the dream but selling something below the dream, which is not very inspiring. Even though most guitars bought are not so-called premium guitars, much of the human condition is the drool factor. It's the 'I'd like to earn through my skill, the justification of owning a premium guitar'. That kind of thing.