Big projects are considerably more specialized to maintain. You don't just need a guy with a pressure washer, you need someone who can get a whole rig hanging over the edge of the building. The plumbing, elevators, fire suppression, trash collection, heating and cooling, and electrical systems require specialists.
They also centralize poverty, which has effects on the local area. The workers in those buildings need to travel all over for their work.
Small, two to four story apartment buildings can largely be managed by handymen. They can be distributed throughout a city, placing them in communities that can support them. The people who live there can work in their local communities.
Beyond that, their initial capital costs are lower, and it's easier to find land that is zoned for 4 story buildings than 40 story buildings.
> Isn't Amazon cheaper than your local electronics store?
Cheaper? Maybe. Better? Absolutely not. Amazon might save me a couple bucks, but the hassle and time dealing with quality control issues, poorly managed inventory, lack of local experience, etc makes the dollars I save disappear I into increased headaches.
The thought of renting a home from Amazon vs the local bookstore is nightmarish to me.