I have never had this issue with my LFS. Although, my LFS closed down for business soon after I purchased my first Betta. I was going to get my fish and as they were bagging him (long time ago, was a little inexperienced), they asked if I had a tank set up for him yet. I said no and they looked at me and said that they can't sell me the fish as the bag only had an hour of oxygen [not true, they were a bit silly on that part, but they were doing it for the wellbeing of the fish]. They asked also if I knew what the Nitrogen cycle was, and I didn't but they gave me a bottle of Quick Start and I left, a little discouraged. Then I went to Petsmart and picked out a 10 gallon Grreat Choice with a filter and hood, which I'm surprised I did because I knew nothing about tank size back then, I just thought the small tanks looked ridiculously small. I picked out some hiding places and a clam bubbler as well, and the lady was helpful and told me I needed a pump for my bubbler [again, inexperienced] as she owned bettas herself. She then pointed out some Tetra pellets to get, I was going to get two bottles but they said it'll last for a while...and it did.
So I went home, set up my new tank, and put in the Quick Start. I didn't have dechlorinator because my well water doesn't have any harmful chemicals or chlorine [thank God...I didn't know about dechlorinator back then]. A few days later, we went and picked up my new fishy, that was Milo! He did wonderfully, until I realized he needed a heater and stole one from my dad x3. Regardless to say, I myself wasn't misguided here in Virginia by the pet store employees when I first started, I got decent information. But also my Petco cleans their cups twice a week [better than most petcos] and uses the Python siphon to clean out their fish tanks.
I've never had a bad experience with employees, but that's probably because I'm around such fish dedicated stores, even the chain stores. The manager of my Petco loves fish and has many fish herself so I'm assuming that's why. Not all chains are bad, it's the people running them.