There are people who can't save up for a down payment and therefore wouldn't be able to responsibly take care of a house even if they were given one.

There's people who don't want to own a house. A house comes with a bunch of costs and responsibility.

• Your furnace goes out in winter, bam, that can be an expensive service call or several thousands of dollars to replace.
• Your sewer line backs up because of tree roots on a Sunday or holiday and now it's several hundred dollars to get a drain company out there.
• Need a new roof? That's a $5,000+ expense all at once.

These are just a few examples. There's quite a number more. Some people like knowing that expenses like that are covered by someone else.

In the grocery store example, there's people who like growing their own food. For others, they'd rather someone else do that even if they're paying a markup to buy it from a grocery store, because they can get everything in one place.