An asynchronous test is definitely more flexible for all parties, but it also means the employer can more forward with far more interviews than they would be able to do in person. Leading to more candidates wasting their time doing nonsense work when they have proportionally less of a chance of getting the job.
Possibly I'm just bitter because of the time I spent 4 hours on a take-home only for the company to ghost me (name-and-shame: Instacart). But at least for in-person interviews they have to buy you lunch before the ghosting can occur.