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.
You’re getting into the weeds about the definition of “work.”
Any definition of “work” that excludes calling, writing applications (AKA writing reports), emailing, interviewing (AKA meetings) etc. also excludes many paid positions.