Interesting to look at the latest ORR passenger figures for stations on the S&C, which someone(s) has kindly put on the Wikipedia site very quickly. Most stations have seen growth on the year 2022-23, and quite a few are above the 2019-20 pre-Covid figures - but not the two key stations, ie Appleby and Settle, which still have some way to go to fully recover.
Armathwaite has done quite well, but from a lowish base, of course - unless there is some short faring going on.
Interestingly, the third busiest station on the route is Gargrave, with 35,000 + entries and exits - which is a wee bit better than Kirkby Stephen, which I think has 'traditionally' held third spot. (OK, Gargrave is not strictly on the S&C, but you know what I mean.)
Anyway, while the trend for the intermediate stations is positive, unless there is evidence of growth between Leeds and Skipton to Carlisle that we can't see, I can't see any rail operator pushing for more trains on the route just yet.
EDIT: Just thought, maybe I'm supposed to put a link up or I'll get a rocket from the controller. Here's Appleby
en.wikipedia.org