Error budgets are to control the workload of the guy who is holding the oncall pager, who otherwise has no say over his or her situation. In recent years companies have shifted to 'you build it you own it' and the infra has been abstracted to the point that the SWE can own the entire thing.

Error budgets also only matter if you either give a shit about your guys or have to pay them for that oncall time. Plenty of employers are happy so say 'salary is exempt, suck it up lol' so errors are effectively free.