Modern trade means complying with regulations. In regulatory terms, EU and US are the superpowers, but the EU more so because US has greater difficulty passing federal regulations. That's an essential but usually overlooked Brexit basic...
50% of UK trade approx is with the EU, plus a few more % with others tied to the EU. Divergence from EU regulations probably means new barriers to that trade. Barriers which inevitably many businesses will wish to avoid, so will argue against.
Now we also want to export globally, and putting up barriers to the EU could help lower them to other countries. The US in particular. But for any given regulation, given the choice, there is likely to be more value in staying close to the EU rather than diverging.
Added to which the EU can set the global regulatory agenda as we see on data / GDPR. We now see companies not liking it but accepting it as the basis for global activity.
Where this leaves us, in summary, is that we're likely to stay close to EU regulations whatever our future political relationship. But those thinking about the latter would do well to bear in mind the former, how modern trade works.
Postscript - the regulatory nature of modern trade doesn't mean you can't look at better regulation or deregulation, but you need to do this carefully bearing in mind the potential costs of divergence. But there may be opportunities for the UK in selected areas
