Tiafoe also became the first African American to reach a US Open semifinal since Arthur Ashe in 1972.
This made me check James Blake, who made the US Open QFs in 2005 and 2006 (and the AO QF in 2008), but never a slam semi.
You mean best of 5. Oh god that could get really ugly. I am more concerned they will at some point move the Mens to Best of 3 which would suck
I did a deep dive on the 3-vs-5 divide a few years ago, and as best I can tell, the difference persists primarily because of TV schedules: if they had all the women play best-of-5 for all the rounds, they might not be able to get all the early-round matches in in their time window, but in particular they wouldnt' be able to get as many matches into their TV windows.
However, that shouldn't preclude them from moving to best-of-5 for at least the later rounds (say, R16 and up), when schedule congestion is much alleviated. I hope they'll do that. There is absolutely nothing athletically that would prevent women from playing best-of-5.
So the persistence of the divide amounts to "historical reasons, plus maybe some minor logistical ones, bolstered by a well-known history of sexism throughout the game".