Yeah, those who need to travel to other towns/cities for work, can easily take their business elsewhere and not flout the rules of essential travel only. But those who don’t, suffer the most. It’s a lose-lose situation and I don’t think it will likely reduce transmission to other towns/cities (it may even increase it).
I know Germany was mentioned earlier in the thread, but the thing is that it’s not as centred around one city like the UK is around London. London house prices are not affordable but that’s where big money can be earned. My town has affordable housing but most jobs are minimum wage here. So I need to travel to London to earn money there. So, a local lockdown for me would be a minor inconvenience and I can use the facilities in London. Whereas in Germany, I’d likely live and work in the same city, so it’s a different situation entirely.