I’ve worked at four private companies and two of them had me sitting around useless for the first week waiting for a computer

Could be my company too, sometimes.

HR has a knack for sending the "incoming employee, user account plz" notice the day before said employee is supposed to start, or sometimes on the day they start, or even two weeks later.

Cue the enraged calls to IT by a manager that's (usually) just as faultless as our user management team (unless the manager also submitted paperwork too late)...