it's just a matter of taste and use case . This is like asking why some people listen to rock music instead of jazz .

Some people need their headphones for sound isolation bc they're not in a position to play music loud where other people can hear it.

Personally, I don't need to spend $1,000 on a headphone or speaker, I'm more than satisfied at a much lower price point with both. I actually have some headphones and some speakers because they serve different purposes.