Dude..as someone who's worked at a fish shop...keeping them in jars is not that big a deal. When people on this forum breed their bettas, what do you think they keep them in? Do they go out and buy gallon bowls for each and every one of the 100 bettas they spawn? Nope. If the jars weren't clean or the bettas were sick and unmedicated, that'd be one thing.
As for bettas living in potholes and such. Yes...yes they do. They don't *just* live in rice paddies. They live in any puddle they can find. They don't go "* flop*flop*splash* Ok...is this a rice paddy? No? Its a pothole!? Well I'm not living here!" If there is the slightest bit of water, thats where they live. Keeping a betta in a small jar long term is horrible, but from my experience, the bettas you see at the lfs aren't there for very long.
Dude, I hate being the bubble burster. *cries*
*blood boils*
just walked to town and on way down went in lfs where I got my 2 girl bettas....neither of them are well....I looked in the tank where they had been a week ago it contained one plec dead and half eaten 2 bettas both got white spot and half dead...and two dead females. I said to bloke serving those 2 bettas I got from you last week are both in a terrible state..have you had any complaints from anyone else..he said no what was I treating them for..told him..he said well you probably got a filter in they dont like moving water...I said I hadnt...I told him my 4 boys are in excellent condition so I think I know what I am doing..I then told him the blue female has got stress stripes..not breeding stripes..so I know she is unwell..at this point he said I better serve this gentleman and disappeared. 
sorry to pinch your thread and rant but feel better now. 
