I'm playing as a thief and breaking into people's houses, but I realise lots of things in people's houses are not owned (i.e. no steal tag), even coin purses or valuables like staffs (some do, but not all)

So I could just go into someone's house, take most of their stuff and they just walk around like normal. I remember in Oblivion everything had an owner except for some houses related to quests.

It kind of makes the game less immersive for a person role playing thief.

I hope they add back ownership to things (at least all the gold and valuables, but preferably everything).

actually, you have become a friend to them, and they let you take stuff from their house/store/etc.

so quit being a friendly sneak-thief.

I started a new game and it was still like this...

Unless I'm a naturally charming wood elf thief? lol

I've just noticed this recently. I could take everything at an inn. I traded with an alchemist and found I could take about 80% of her things. Some potions, but not all. All but one or two ingredients.

The town square merchants' goods were stealable, but now I'm finding I can take the food seller's goods. In a way, it's almost less fun if I just own the damned town. It's already silly that I can empty out a farmer's field while he sleeps.

Yeah I've noticed this too. At first I chalked it up to the person being my friend, but some of the houses I broke in to were owned by people I've never done a quest for...

It's not silly; because you can sell those picked plants back to the farmer.

That isn't silly either, because you're getting paid for the work, not the items themselves.

I can sell them, yes, but I don't. It's not a bug; it's just a moral issue. If I harvested all the crops at a real farm and kept them, it'd be stealing. Essentially, I'm just taking everyone's food. On the other hand, they don't need it because it magically refreshes, anyway. (Hee, even at Faendal's, with no one there. More food, potions, gold...)