> For example sharing a flat with 6 people is sometimes half the cost of 3-4 hotel rooms (depending on how you can split)

And, again, this is the whole problem. Because that's a flat that could have gone to someone who actually lives and works in the local area, not a tourist. It's cheaper because it externalizes that cost.

I'm fine with hostels too, I see no problem with people choosing them. I'm not fine with converting residential homes into unlicensed hotels . It destroys the local community, and drives up prices for all the other people who are left trying to live there, and further feeds housing crises.