There are a lot of potential reasons.
Here’s a thought: consider the potentially analogous case of performance-enhancing drugs for athletes. The drugs unambiguously make them better at their jobs, but the drugs have severe long-term health costs and wreak havoc on the fairness of the playing field. It’s easy to see why an athlete might choose not to use them, even when others are.
Of course, those negative factors alone are not enough to dissuade people en masse who want to get a leg up on their competitors, so the use of performance-enhancing drugs must be further restricted by institutional bans.
There are rules against using performance enhancing drugs in competitive sports, because ultimately the goal of the sport is entertainment, and the entertainment value increases with a rule based even playing field.
Business is not like this, because the value of what a business does is in its actual output, not in its entertainment value for spectators.
Of course there are other rules (legislative and regulatory) that apply, for other good reasons. But their goal is not to create an entertaining competitive environment, but rather to control externalities of what companies do.
I favor AI regulation, but I also don't think treating it like a performance enhancing drug would be a smart way to regulate it. Higher business productivity is useful to society in a way that breaking home run records is not.