[dventimi]

"the only reason it’s believed to exist at all is because a lot of otherwise well-understood equations and observations require it to exist."

I mean...those are pretty good reasons. If a particular theory successfully predicts more out of "a lot" of observations than any other competing theory does, and is a smaller departure from "a lot" of existing theory than any other competing theory is, would you choose to spend your career researching those competing theories?