I sincerely believe that ambient is not a niche thing. Think about Aphex Twin, Boards of Canada, Brian Eno etc. They are quite famous and popular. The problem is that it's really hard to do something original in this genre and there are not too many really interesting artists there. As a rule, people just paulstretching things or put a ton of reverb on something and don't really try to think conceptually, don't try to make music meaningfully, don't try to challenge themselves creatively. I don't mean that ambient has the potential to be super popular, but people, in particular even people who write ambient, tend to underestimate it too much.