We already do with legislation that requires severance packages and tax benefits for hiring. Many countries go much further.
One might bring up the personal consequences bourne by surplus employees who're then laid off during the unavoidable corrective phase - or is that not something society should care about? What are you optimising for?
> There’s no reason we couldn’t decide that we want to err on the side of employing too many people.
Yeah that's not how a company should run.