I see the value of UX, and I haven't decided how important it is to me yet. I do feel like the conversations in tech circles seem to be overselling its benefit

I see the value of UX, and I haven't decided how important it is to me yet. I do feel like the conversations in tech circles seem to be overselling its benefits. I get skeptical when hearing bold, blanket assertions like "A UX person is one of the critical components of a startup today. You need a [hacker, hustler,UX person]". I don't disagree that some startups need a UX person, but that flavor of claim strikes me as overreaching, and possibly just UX guys talking up their book. /not saying this is necessarily the case, but I can't tell that its not/ Specifically regarding the Hipmunk case, since its often cited as an example of how newcomers superior UX/UI can oust established players: Why are non-Hipmunk sites still in business, or even more, why are they still the dominant players in the market? Its undeniable that there are examples of "bad UX companies" succeeding and "great UX companies" failing. What experiments can be/have been done to isolate the impact of just UX as a contributor for startup failure/success? (I don't consider "split testing UX on a given site" sufficient. This generally finds local maxima and incremental improvements to the business. It generally makes you succeed more or less, but I want to hear about why the UX guy is a critical pillar to the existence of a company (and then, most companies))