If not liked by delta STs, to me it represents what "we" are looking for or like, in a certain way, that embodies 'the type'.
It has to do with a smoothness.
Often times an element of non-relational focus
Or if there is a relational focus, it is subtle and positive, gentle (ala delta NFs)
Usually reassuring, too.
But always smooth, and 'comfortable'.
At least that is the kind of stuff that is music that makes me feel like I can relax. Sometimes it's just good 'background music'. But it's definitely something.