Portland to Santa Clara is a relatively flat drive. LA to SLC is not, plus a fully-loaded Model 3 in extreme weather (at least, extreme for EVs) and the need to charge multiple times on the way due to charging anxiety related to the lack of chargers en route, the overnight stay in a motel due to the delay related to charging...yeah, it's over 24 hours, easily.
You might want to consider that not everybody is driving themselves; some people have families with them and that changes the calculus of how you approach the drive.
Eh...I just went to ABRP, told it to map me from LA to SLC, assuming 500 kg (1,100 lbs) of extra weight, 0 C temperatures, and some extra range anxiety (Arrive at each charger with at least 30% battery), and it STILL only estimated a total of 12 hours.
You might want to consider that not everybody is driving themselves; some people have families with them and that changes the calculus of how you approach the drive.