I've tried having a regular fish tank (goldfish, assorted tropical freshwater fish), and they never lasted very long. I'm sure I did something wrong but I never figured out what specifically.
Then there's the betta. Very easy to care for. They just need to be kept separately. They can live without water filtration or difficult environment adjustments. Keep their (easy-to-treat) water fresh and their container clean, and they're happy.
All the bettas I've had have lived a long time. They do have a lifespan so they eventually must pass. But while they're around? They're a pleasure. Graceful, beautiful, pleasing to the eye. Very tempting to have a lot of them.