Xcode was recently upgraded to 13.2.1 and since that happened I no longer see any simulators on the components tab.
I recall this happening once before with 12.09.1 and hoping it's the same silly issues with Apple's servers just returning a 401 and it's a simple fix.
I uninstalled xcode and reinstalled it and still nothing.
I was having this problem, and it now seems to have fixed itself.
Xcode is now showing the Simulators, as expected.
See the original thread:
https://developer.apple.com/forums/thread/696830?answerId=699203022#699203022
Xcode 13.2.1 (13C100)