Not CPU costs, processing costs. Password resets are actually quite expensive. Microsoft and Google pushed the FIDO Alliance toward widespread use of a passwordless login credential because it benefited them. Google and MS get tens of millions of password resets a year. So if each one of those cost them $2 (some companies spend as much as $70 on each one if a human is involved), that's literally tens of millions of dollars saved. Then you say "oh, for security" as the tie-in to not make it about your bottom line.

https://www.authx.com/blog/how-much-does-a-password-reset-cost/ https://journal.jadaptive.com/the-true-cost-of-password-resets/ https://www.m365.fm/passwords-are-broken-passkeys-fix-everything/