As VHG points out, it is the 'trapped' ethos that sets up the comedy, and is always a factor in a great comedy.
Think about Fawlty, Hancock, Meldrew, Brent, Perrin, all people who are trapped and railing against their situation.
The poignancy of the Steptoes is their mutual loathing / dependence, with Wilfred Brambell's wonderfully mobile face, some of his pathos would not be out of place in Brecht or Pinter.
I rememebr watching one b & w episode and realising after that it had all benn shot in one room, on one camera, with no edits, so it was in effect a one-act theatre play. That was the genius of the form, and the players, so now, I don't think it will come again because audience tastes have moved on.
It was not 'un-PC' because such concepts did not exist at that time - and tv comedy was better for that.