Pool stores are in a business that is involved in a changing model, many just don't understand it. First, they are at a disadvantage in that most have a limited season. It is only very far south that a store can truly expect 12 month sales to support them.
Second, they are competing in the same labor pool as everyone else, paying minimum wage for the most part. This severely limits their employee choices, a lot of time to those who can accept the seasonal work - high school/college kids.
Third, limited training other than "on the job" which results in a lack of understanding on the employee conducting the tests. What training may be available is more sales training conducted by manufacturer representatives who are really just teaching how to sell the latest product.
Forth, the Internet. Not only the knowledge from sites such as this but the availability of products with next/second day shipping at less than what the brick & mortar sells it for is cuttin into their sales. As an example of this last year I needed a new light bulb, 500watt. A quick Amazon search showed it at $17 and two day shipping with my Prime membership. I am an instant geatfication kind of guy so I thought, a pool store purchase! I ran down to the store and the only thing they had were 400 watt bulbs (they explained it was all anyone needed) and they were $39. Now, I've run businesses before and know they have to keep the lights on. I'm willing to pay a little more for,them to have it there on the shelf, and heck my pool isn't so large a 400watt bulb won't work. I talked to the manager about the price and even mentioned Amazon. They did not discount, take it or leave it.
I go to one of several pool stores a couple of times a year. One store really likes me because I purchased my M5 from them as well as a Hot Springs spa. I get my water sampled to see if they do it right and to listen to the banter in the store. I don't think all or even most pool store owners are evil trying to keep your pool green to increase sales. They are just very poorly trained and informed. They don't know that that fancy AlkUp is just baking soda.