I'm going to start this entire thing by saying, I personally can't. I understand how some people can make a good case for keeping certain ones and do justice to the animal but it's really not for me.
I have a friend who wants to add denison barbs to their 75g, however they're a species that is endangered due to the aquarium trade and it doesn't sit right with me keeping them in captivity. I guess the bonus question is, how reliably can people get captive-bred specimens? This feels like a really ethical gray area.
I'm not trying to receive validation or virtue-signal here, I'm genuinely curious about the opinions of others on the topic. Environmental health is a really complicated subject and like with most things aquarium related, I like to receive as much information as possible and then draw my own conclusions.