How do you quantify "incentive"? Is a landlord really looking at 5% lower property value and deciding it's not worth investing? Is this even true in aggregate?
I think of how I was absolutely shocked when a Big Mac meal was $10 during the pandemic (I think it cost about $2.50 the first time I bought it) and didn’t think I was going to buy 4% less of it but rather I skipped the fries.
See what happened in NYC regarding the consolidation of housing units.
The cost of the wood and the labor needed to build the house is unaffected by the rent control, so if cost remains the same, but the reward (or "revenue") from building the house decrease from $100K to $95K, then fewer houses will get built.
When supply is constrained by the availability of builders and materials, then some landlords dropping out won’t make a lot of difference there.