It's currently not implemented. I'm sure there is some technical issue they need to solve. Since most other things are able to be gifted, ZOS will likely allow houses. There is money to be made off of it. Just need to wait a bit until they put it in.
If you gifted someone a house and they either refused it or already owned it, you'd be forced to give it away to someone else. You wouldn't just get your crowns back. I suspect they're trying to alleviate a lot of potential headaches here.
That being said, if you really wanted to buy a house for someone, you could probably open a ticket and have them manually do it. Don't quote me on this, though.
I heard that people sold houses to other players by contacting the support as well. It would go down like this, the person with the crowns buys the house for themselves and then contacts the support to transfer ownership from one account to the other. However this is all second-hand source so don't trust me and ask the support about it before you buy.
This Bosmer was tortured to death. There is nothing left to be done.
Honestly, I'd rather see them add 100 bonus crowns to a 6 month subscription with the benefit upgrade next month.
That makes it an even 10,000 as opposed to 9,900.
Then buying a long-term subscription for somebody (through a gift card or other payment type) nets them enough crowns to get a furnished house in the Tel Galen or Hunter's Glade range.
But whatever the reason, I'm okay with houses being off the gift table. It puts everyone on equal footing to get it instead of being able to casually throw 3 million gold into a crown trade just because I've played the game longer.