Its not that simple
Even if people are more productive in less time, that doesn't mean you can earn the same money. Many businesses operate on "hours spend" per task. As an example, let's take hairdressers. If your hairdresser is now working only 6 hours instead of 8, that's a potential 25% loss in revenue. And they won't be magically faster now just because they work less. So if salary reduction is not an option, the only option is increasing prices.
What you're saying is fine for office jobs, but just not an option for most service jobs. Waiters aren't magically going to serve tables faster, cashiers won't make customers move faster, etc.