I read it alot online but the few times I tell them something it does no good as they just come back with ignorant and rude remarks about how I don't know anything about bettas and they know how to take care of a fish and blah blah blah. Some people are just unwilling to learn anything.
I also have heard store workers telling people those things and when I can, I politely interrupt, or catch the person before they buy anything to let them know that NO... a 6" bowl is entirely not enough for a betta.
I actually have had a few people change their minds and tell me they would buy a 2 gallon tank instead, after I talked to them. 1 store worker said that said she was glad to learn that, since she got minimal training... and she said she'd be sure to tell future customers that (that made me really happy).
Though I've had bettas most of my life... when I was younger and they were really mom's bettas... they didn't have the most ideal conditions. They weren't in tiny betta bowls but they could have been better off. Mom insisted she did her research and new how to care for them and why not trust mom, right? (everyone in our family is an animal lover). They had a 1.6-2 gallon tank, glass bead substrate, a castle (that I still have and use) no filter, no light, no air stones, and no variety in their diet. Their water was changed 100% every time and the glass beads washed. Mom didn't know anything about good vs bad bacterias in a fish tank and all that.
When I got my OWN bettas I did excessive research and pretty much learned to ignore any advice she gave me. She tried to convince me that a filter, air stone, and heater were 100% unnecessary. Then when I showed her my purple/copper double tail betta she exclaimed that she didn't even KNOW bettas came in colors other than red and blue... or that they had any tails other than veil tails.
She doesn't have bettas anymore. She was talking about setting up a salt water tank but when I told her what was needed and how to do it, she changed her mind really fast (in my opinion, it's really nothing hard if you know what you're doing... but I guess she thought fish were no-maintnance rather than low-maintnance, lol)