Yes, one of the accounting bodies started warning a few years ago about the proliferation of barber shops being a front for money laundering.
The only way I can think to police it, would be for tax inspectors to stand outside and count the customers!
In fact that's exactly what large enforcement operations against these do, the problem is that they just close down, the person who they were registered to disappears(if they ever existed at all) and another shop opens in the same place registered to someone else. It's a game of whack a mole.
It's just stupid that councils have no problem arguing that say, Clarkson(sorry, stupid example) can't open a pub in a town with no other pub or other employment opportunities, but 17th vape shop on the same street is fair game and free market.