Wimbledon did have pre-qualifying from 1983 to 2003. In the later years numbers were restricted to ranked players and LTA choices, but I vaguely recall in earlier years that you could just turn up (and presumably pay a fee) to take part to win one of 4 qualifying WCs, and some park players did do so. The big difference was the lack of publicity, so most people weren't aware of the possibility or didn't want to travel to London on a weekday.

The US scheme looks more democratic though - and I don't associate the LTA or Wimbledon with democracy!