Because that's extra work and risk for a small return, plus local ordinances might not even allow it, or would make it difficult. Being a commercial landlord isn't that easy. And there might be "demand", but not at the prices being offered.
As with many things “not profitable enough” is a huge detriment to society and a huge flaw with unchecked capitalism when so much wealth accumulates at the top
Here's my low-effort snarky response to your question: Pesky Laws, ordinances, labor rules, and MBAs with fancy graphs that say something is "unprofitable".