E.g. it probably is encouraging for the weakest startups to have some kind of shared workspace they have to come to every day. But for the best startups it's not only unnecessary, but undesirable. Larry and Sergey would not have been better off in some kind of shared workspace. Their garage was the ideal place for them.
The arguments pro and con for shared living space seem to be more extreme versions of the arguments for shared workspace.
If we have to choose between helping failures become small successes and helping successes become big successes, we'd prefer to work on the latter.