I gave 2 good reasons why someone would have a second home. If you mean purpose, not everyone who owns a second home rents it out, and not everyone who rents it out is doing it for fat profit.

My uncle owns 2 homes. One he bought with my aunt, and one he inherited. His brother lives in the second home for various reasons and his end of the deal is that he takes care of it. I have another uncle who bought a studio apartment with my aunt maybe 30 years ago, and they mortgaged a new apartment some years ago, when my cousin got too old to sleep in one room with them. They rent out the studio to college students for what I think is a fairly low price. One of them is now retired and they've got a good chunk more time to pay on that mortgage and prices have skyrocketed in their area. If shit goes south financially, they have a backup place to live in their old age.

I'm an immigrant myself and I can tell by the way prices are going here, I'm going to need to find a spouse to mortgage an apartment if I want to buy anything. I don't think anyone in those situations is some kind of monster for not selling me their second home.

I think a remote vacation home or cabin or whatever is also a legitimate reason to own 2 properties. I also think hotels and motels fall under owned property, and I think those are legit too.

Like I said, IMO the problem is with people hoovering up properties specifically to inflate prices and to make profit by doing nothing. It's rentseekers and bad landlords, not multi-home owners.

Edit: the relationships here read kinda weird. Both uncles are "by alliance", married into the family. Of course, they both share ownership of the stuff they bought with my aunts, but idk how the inheritance works, and I'm not gonna ask. The way it's phrased in the family is that he inherited that house in the countryside and his brother (which is like distant family to me I guess) lives there.