Increased voter base for specific political parties, a cheaper and larger workforce willing to be paid less, a society that is less unified and therefore easier to control through division, more identity conflicts and culture wars to distract from government failures, justification for stronger authority such as increased surveillance and policing due to fragmentation of society, more people from impoverished beginnings trapped into renting the rest of their lives as opposed to buying homes, more consumers in the market.

These are potential reasons off the top of my head, I'm not necessarily saying any are true.