Back when this show was written (80s/90s?) I'll bet there was a much bigger 'street' sex scene than now. Even if you just look at Soho - the uBer area for sex and adult work - back in the 80s/90s (and much prior to that, back to 60s) there was a thriving sex scene; not just street walkers and walk ups and brothels, but all the other adult establishments that inahbited the area. Peep shows, strip clubs, XXX adult shops, cinemas, adult "book" shops, lots of women and lots of sexual intent within a small area, the pubs round there must have been regular haunts for pros and clients.
It's nothing like that now.