Trying to appear upmarket may be part of it, but the policy is not formalised and has been implemented aggresively seemingly at the owner and his daughter's discretion.
It's not even a door policy, they will even start taking orders only for the management to tell the staff to stop. They have kicked out pregnant women, businessmen, people of varying races, one member of a party after eveyone else has settled in and people of dissability with no formal justification or obvious reason. The only logical conclusion is that they are on an absolute power trip or completely bigotted. And now, their clientelle has spoken.