A Hogarthian setup is half the cost, and learning it provides useful insight into how to set up any BCD, how to choose one, what you like and what you don't. Learning with the Axiom has much less knowledge carry over.
The cost of a BP/W is not necessarily less expensive than jacket/vest style BCD, and there are some basic jackets/vests that are less expensive.
There is also the issue of lack of standardization for fit of components across brands. While those of us who have adopted the use of BP/Ws often espouse how customizable they are, for those who have little to no experience with them, buying components to make a "customized" solution is a gamble with regards to whether those components will work together.
Most new divers that I have come across are not looking to get into the technical side of gear when they begin their journey in SCUBA diving. They are not interested in knowing how they can customize the position of a D-ring and tri-glide down to the millimeter. They want something that is fairly comfortable, easy to use, and easy to adjust. Unfortunately, while the BP/W may fit this criteria, optically it tends to fail as it appears uncomfortable, looks and can be a pain to set up and adjust, and the cost for an adjustable harness itself tends to approximate the price of a jacket/vest bcd.
Telling a new diver that a BP/W is customizable and limitlessly adjustable as a selling point tends to fall on deaf ears, as they have no idea what their needs are. Even among divers with a modicum of experience, I have lost track of how many posts on SB I have come across where folks are debating the amount of lift they should go with, for a new diver this type of thing just makes their head explode.
There are four divers in my house and we all are outfitted with BP/Ws, but when I bought mine before the others got theirs they looked at it with skepticism wondering how it could possibly be more comfortable and were surprised that it was not uncomfortable.
One thing that was nearly a killer for my wife and daughters was the pain-in-the-arse factor of getting their rigs to fit properly. First there was the initial fitting once the harness was attached, then there was the fine-tuning with their wetsuit on. Putting a wet suit on and standing around in it is not very comfortable for a good number of people, and the time it took to make adjustments to the harness, test the fit and try again doesn't make the situation better. After repeatedly test fitting webbing adjustments, one then has to fine-tune the D-ring placements and other accoutrements. Finally one then has to test fit with a tank attached...and ultimately one will not know if it fits correctly until they test the fit in water, which is not often conveniently available. If one has to rent tanks and weights then there is a cost just to get things to fit correctly...and I will say that even after a handful of years of use a BP/W I am still messing with how mine fits and functions, BUT I like that sort of thing AND I know that my wife and kids couldn't care less about having the ability for infinite adjustability and customization....they don't want to enjoy equipment, they want to enjoy diving. Add changes to exposure suit thickness or type (wetsuit/drysuit) and for someone who does not care to muck about with gear the BP/W is kind of a huge pain in the arse compared to a jacket/vest, especially for that someone who is an occasional diver.
For me, the greatest benefits of a BP/W are durability and modularity...if one aspect of the system fails I don't have to replace the whole system like I did when the sonically welded inflator flange of my jacket BCD separated from the material.
I think that one issue for shops is that they have to "convince" clients that they will be comfortable and better off with a BP/W, that takes time that doesn't always result in a return on investment for the shop...in this regard jacket style bcd's don't need much of any explanation, and the major selling points that differentiate models and brands are not whether it will fit or be comfortable but how gucci the features are. One can pull a jacket style BCD off the rack or out of a box and directly try it on and be "convinced" it is comfortable...one does not need to stand around the shop while the shop staff faff around with the harness just to get it to the point the client can just try it on.
All that being said, I would still recommend a BP/W over a jacket/vest style BCD, but in my experience, new divers tend not to care how their BCD goes together, they just want to strap it on a tank, connect the LP inflator hose, don it, and splash.
-Z