Zone 1 - zone 2/3 is not bad, but what actually happens is people are moved from zone 1 to some random town 40 miles away (because it's WAY cheaper to do that).

These people don't have cars, they are the least well off people in our society, often physically, mentally and materially. Their entire support system, friends, family etc. are ripped up from beneath them. They end up never rejoining the economy and the cycle continues.

These are people so we can't just shift them where we want to.

Here's an example from Zone 1:

https://www.standard.co.uk/news/london/residents-of-the-heyg...

These people OWNED their flats, they were compulsory purchased from them at ridiculously low rates, demolished and replaced with luxury flats. The only option for these people was to move from their 2 bed flat to a new studio or leave London.

Some of the most expensive places in London are outside Zone 1 (Hampstead, Richmond, Kensington, West Brompton, Wimbledon, etc.). Also creating a high density of social housing aka ghettos is not desirable for any city in the world and those who have it have big problems because of it. London has huge inequality problems, but the fact that you can have a millionaires road only 5 minutes away from a council estate has the advantage that social issues are not just being ignored and brushed under the carpet by forcing people as far away as possible, it creates more diverse and accepting communities, it ensures that people from all different fortunes have access to nice parks, good transport links (which are even more important for people who are on low income), etc.

I don't think it is very nice to make the assumption that a high density of social housing will result in a ghetto. Do you have sources that people in social housing are more prone to violence and crime?

It's neither an assumption nor about being nice. As mentioned isolated dense social housing has been observed to create conditions that alternate plans can counter. It also doesn't have to be about violence or crime--mere the neglect of neighbourhoods that are not 'in mind' of decision makers for simple things like maintenance of roads, lights, etc all contribute to this.

Ghetto doesn't imply violence or crime to me. Per Wikipedia: "A ghetto is a part of a city in which members of a minority group live, typically as a result of social, legal, or economic pressure."

The large council estates in the UK often were an attempt at pushing poor people out to cheaper areas in many cases. Even in zone 1 most of the council estates that still exists are there because those areas were cheap, deprived, often bombed out hellholes in the post war years, and so were a convenient place to build cheap council housing.

It's just that they've now become desirable locations.

Continuing to move people out whenever an area becomes desirable is a deeply anti-social and very much temporary solution, and creates the new issue of dealing with the fact that a lot of the jobs are in the centre and a lot of the people who need this housing can't afford to get to them if they need anything more expensive than a bus pass.