[hnick]

It's just a different risk profile. They see themselves as good at managing multiple properties for a steady income, rather than leveraging highly and managing just a few for an uncertain outcome (markets change for better or worse and they don't want to be left in the lurch).

Likewise, airlines use a lot of fuel. They could save money by buying fuel producing companies... but they're not in that business and don't want to worry about it. You can vertically integrate but you also have to recognise what you are good at and what you want to focus on.

There are REITs (Real Estate Investment Trusts) by the way, but they did quite poorly during the GFC in Australia at least.