Incentives aren't needed, and governments are not typically effective at out-guessing markets which it comes to what works and doesn't. What is needed is to remove disincentives and distortions.
Whether or not regulations favour single-family is less important than the fact that families favour it. The insistence of authorities to shape the winds and tides (people) is at the root of much dysfunction.
Any kind of subsidy will distort market behaviour. Every scheme to produce "controlled" units means someone must choose who gets one and who doesn't, which is an opportunity for corrupt behaviour.
This presupposes that the market is the appropriate mechanism for 100% of the problem. The challenge with that is that ‘the market’, left to its own devices, will seek to maximize profit and has no overriding vested interest in ensuring pretty much everyone has access to a safe roof over their head. That leaves people at the bottom of the wealth scale shit out of luck, with real property increasingly accumulating into the ownership of a smaller proportion of wealthier people or businesses. And I say this as someone who ‘won’ this game, with about 1/3 value remaining on the mortgage of a very nice and large fully detached house that has doubled in value, as well as a rental condo unit that we fully own. If mortgage rates were lower, we’d consider a second one. We made it, and my pure selfish best interest would be to take the same stance as you- but I don’t feel ethically able to do that. I have family living the other side of this coin and it sucks.
We have these things because 1) we both have good jobs, and more importantly, 2) my wife’s parents died very prematurely and she inherited her portion of pretty good equity. This let us get into the market, kind of ‘just in time’. We couldn’t repeat that to nearly the same extent now.
The rules of the game favoured us. They don’t favour a lot of other people. The market doesn’t really care if you have to pay half your take home income or more to make rent; as long as someone can pay it, landlords will charge it. Just as the market is fine with there always being a certain percentage of people unemployed, so too it’s fine with a certain percentage being unhoused, until and unless it becomes an
economic imperative to change that.
So no, as proud as some 1800s economists would be of your fervent devotion, this is not an issue that is appropriate to be left fully or even mostly without government intervention in the form of various policies. As a society we’ve evolved at least a bit beyond being ok with people being left completely to fend for themselves. While government intervention is by its nature less efficient, some problems are not amenable to being solved by pure profit motive. Sometimes the cost benefit analysis needs to be undertaken by those with a different motive, and some of the costs need to be shared among those of us with the luckier role of the dice.