I prefer online retailers because there is a lot more choice there. I can't find an inflatable knee pillow in local stores. The supermarket close to me even stopped selling batteries.
This is true. Many "weird" purchases that used to be available from someone local are now impossible to get. Not sure about the supermarket not stocking batteries though... That's just insane.
I work at a grocery store that used to sell batteries. They stopped. If I had to guess, I'd say the number of batteries that were thrown away due to being past the date on them had a lot to do with it. Nobody ever bought them. Everything important is rechargeable these days, with the possible exception of remote controls (which shouldn't need replacement batteries at all: remember solar-powered calculators? Put that on a remote and just leave it face up to recharge when not in use)