While some enforcement may be venal, a complete absence of t would probably result in chaos.
Maybe, maybe not. Outside London many people stop in YBJs in ways that cause no traffic impact at all, nothing is done about it and nobody cares. On the odd occasion that someone actually blocks the junction, for most ordinary decent people the embarrassment of people honking their horns is enough to try and do better next time.
You also have to balance the amount of enforcement that serves no traffic management purpose at all and is just pursued for the purpose of raising money, take for instance red route PCNs where the camera is behind the car so it can't see the blue badge, so TFL issue the PCN anyway without evidence of any contravention and they require the motorist to positively prove their innocence, and then refuse the representations anyway (of course TFL don't care as they're morally bankrupt).
