Hard to explain. It just feels better to be playing something official.
It's because of the brand behind it. There are modders who can make content as good as, if not better, than Bethesda.
I'm not bashing Beth. But I can see no practical reason for a PC player to purchase Hearthfire when there are already mods in existence that provide excellent player homes, some of which you build.
Then again, it's only 5 bucks. And there were house packs like this for Oblivion, too. But I will personally not be buying the DLC as I have no need for it. It's not like Dawnguard, which was full of original content you'd pretty much never see come from a player mod.