Job posts there usually come with a salary range, and salary can be a deal-breaker for a lot of people (most people?), so seeing salary ranges up front for specific companies & positions you're interested in can help avoid a lot of wasted time on both sides due to mismatch in expectations around compensation.
The tool is even more helpful when you're in that initial stage of looking for work but not sure where to apply to yet, because you can filter for jobs that match a certain salary range, within certain locations/industries, level of funding, tech choices, etc.
I also personally really like job searching platforms like Hired.com, Underdog.io, Triplebyte, and AngelList's own A-List that allow you to apply once to their platform and then have companies come to you with offers for interviews, many of which of also require the company to disclose salary range up front so you can decide which offers are worth your time to pursue.