Well no the mind is obviously also not real. It is also extrinsic. And our own mind interprets itself as a "thing". But regardless that wasn't the original subject of discussion. And yes you're right that it serves no utility. I don't deny that. The reason the human brain thinks in "things" is exactly because it serves a useful evolutionary purpose.

In general, it is a hard subject to talk about because our mind constantly wants to categorize EVERYTHING.

Edit: I have a way to explain it better. Essentially our mind constructs are an emergent property from our brain, while our brain itself emerged from biochemistry, while biochemistry emerged from chemistry and so on. They are all extrinsic, and somewhere down there there's "things" (again I use that terminology because our minds are simply limited in that way) that are in fact intrinsic. Electrons seem to be one for example. Meaning there is nothing that electrons themselves emerge from. And again, this might change based on developments in science.