I can't blame brick and mortar retailers. Frankly, look at all the threads on the ECF about which is the best and you'll realize two things.
First, the people who are most motivated to make the best decision are the people who will be vaping. And those people don't agree. So, why would some retailer, who isn't vaping and is probably carrying more than just that product, motivated to sell the best one? They're likely not.
The second things is that the people on this forum are likely some of the best informed vapers in the world and THEY don't agree.
Additionally, my personal experience is that the different styles of attys generally have little impact on what I vape. A 901 or a 510 atty both vape a good juice off of a good battery pretty well. I prefer 510 over the 901 mainly because of the air-hole and mess. But I seldom, if ever, see people ask for "the least messy" atty - they want the one that keeps them off of analogs the best.
But, and here's a big part of what I think impacts it, I think there's a subtle but VERY impacting difference between "e-cigarettes" and "personal vaporizers". We're vapers, we know what make a good vape. But what makes a good vape is (predominantly) NOT what makes a good replacement for analogs. If the brick and mortar vendors were selling good vapes, you'd likely see a few modular parts sold coupled with good juice rather than a device that's called an "electronic cigarette" and vaguely resembles one too.
As to the non-brick and mortars, we'll I think there's also the entire "brand differentiation" thing. A lot of the best vendors on here sell different models of vaporizers - batteries, atties, all that. And they couple it with good juice. I also notice a trend that the vendors selling "electronic cigarettes" tend to sell only their pre-loaded carts, with their branding and only their brand of "cig-a-like" juice. I think it all speaks to that subtle difference between good vapes and fake cigs.