I never understood these type of arguments.
To build a house or a whole housing project, you need to gather things. The first thing would be the blueprints, those could be drops, rep rewards or things you buy with achievement points.
Right now we do gain achievements without any purpose, minus a few titles here and there. They dont come from sitting in our home, they do come from playing this game, every aspect of it.
Same applies to monsters and vendors.
But if we have the blueprints, then we still need the wood, rocks, plants for a garden, fish for our pool… all these “incredients” must come from the real world and they would give the real world finally a purpose.
Right now, we do nothing after we are done questing outside of dungeons or raids. So much content in this game is a complete wasteland, nobody does it, except for a few that hunt achievements or level up.
Housing if done right, demands that players explore things, interact with each other. The professions right now, are honestly useless in most parts. Unless you offer raid supplies, or a rare transmog, your profession is just for you. This housing could change.
To build a house from scratch or a cottage or some other infrastructure, could take months and would require much more from a player in regards of leaving their comfort zone, than any raid or dungeon currently does.
The for me biggest question would be if housing should offer some kind of endgame system, making it a path to progress item wise and if so how would that look like. I personally could think about a follower system or a buff system.
If you sleep in your house, you gain a buff or you could hire a follower (someone you can fully equip), similar to SWTOR. They could lead you into adventures, similar to the solo dungeon we have now, just that you do it with your follower together.
It would never be the best loot in the game, give that to raiders. But it would be an endgame for players not into raiding, which are quite a lot I think.
But this is in my opinion the biggest questionmark over the whole system, should it be just cosmetic or with an actual endgame content type that raiders dont profit from, so that they are not feeling forced to do it.