Yeah, I've been thinking about this too because I've found myself using the RTS more these days than in the past, though a lot of it is still for niche applications rather than as a general sander. Rounding corners for example -- even after breaking the edge a bit with a block plane, there's still a risk with an ROS sander of catching the edge with one of the paper holes and tearing the abrasive, whereas the RTS will perform the task without issue. I do a fair amount of work with the interface pad, and when it comes to concave surfaces in tight quarters, the RTS is also preferable, as it allows you to precisely target the area.
As others have already mentioned, there's also a compatibility factor with the paper -- don't need to get a whole separate line of abrasives for the LS 130, and I can also use somewhat spent RTS abrasive sheets as hand me downs for the HSK and rectangular hand sanding block.
One of the issues I run into though using the RTS as a general sander, is that since the sanding pattern of the RTS is different than an ROS, it doesn't always work to mix them together on the same surface. So it's either all or nothing using the RTS on any flat surface. On narrower stock like for face frames or door rails/stiles I will sometimes use the RTS, but pound for pound the ETS-125 (which can operate quite comfortably on 2" or even 1 1/2" stock) still consistently produces a better finish, so I tend to opt for the latter in those situations.