That does seem like a crap system, but they manage to do income tax bands where you only pay the extra tax on what is over the threshold. Of course it's more complex with a business, but that's what we have computers for!
You definitely don't want your barber to be distracted. Mine does say that the running costs are high. He was operating on his own for a while after someone was taking from the till, but has a second guy there now so they can take more customers. It's a business you can't move online, but I wonder if we'll ever let robots cut our hair?