They say that because owning a home allows you to reduce your bills, but also more crucially and viscerally because owning a home allows you to be free and have a place that is truly yours to do with what you will. You can paint the walls, have a pet, host a party, knock down a wall and build an extension, do whatever you like to make your mark on it and the world. It's yours and if you will it, it always will be. It's a level of peace and security that's almost incomparible. There's a reason in most of history there was a distinction drawn between bonded peasants and freeholders.
Sure you might need a new roof and insurance and taxes fluctuate but that’s a BIG BIG deal as anyone who’s rented and been at the mercy of markets can tell you.
This is even more true now as the rental market (like so many markets) is coming to be dominated by corporate landlord La using revenue extracting software.
It's not an incentive to "not steal the trolley", it's an incentive to put it back in its place for people who were already not planning on stealing one.
This way the store and the customers don't have to deal with trolleys strewn around everywhere and blocking parking spaces, among other advantages.
I think when they removed the coins during Covid they just noticed that most people were already well-behaved enough to return the carts to their places, so the incentive is just not needed anymore. Actually in Belgium, Colruyt had never had coins for their carts and it just works.
It’s also an incentive for anyone else.
If I put the coin in and then leave the cart in the lot anyways, someone who wanders by is also incentivized to grab it and put it back, as they would get a free coin.
The system is actually somewhat elegant, if you return the cart you pay nothing and if you don’t you pay a small fine to whoever does.