Not only does this disincentivize HR from running fake vacancies or stringing multiple candidates on just to keep their options open, but it also solves the problem of unemployed people job-searching effectively working full-time for free. The fact that companies would have to pay to hire workers would mean they try to make the selection as short and effective as possible.
This concept is why I have a deep respect for DuckDuckGo as a company. When interviewing there for a SRE position, the round 2 and 3 interviews included coding challenges. They paid (IIRC) $75/hr based on the maximum time they wanted candidates to spend on each assignment. I ended up not getting the position, but they’re the only company I made it to the final decision step with that I didn’t feel was wasting my time.