Very true edt
Fuels are awesome C kites, it is just that most who are not into hardcore full C kite style has chosen other kites (for slingshot often the RPM) that they can use for a wider "range".
Meaning - it can be used for freeride and touring, it can be used for waves, and it can be used for "freeride" freestyle, and beginners can also use that type easily.
So the RPM (and other SLE kites) covers a huge area, thus preferred by many today.
And some kites, like the North Vegas, is "almost" a C kite, but with a bit wider range - so also liked by freestylers.
Whereas for full-on freestyle the pure C kites are usually the best - but a much smaller minority today, as many can also use kites like the Naish Park for okay freestyle, eventhough not a C kite - but then it has a much broader usage instead
So you are right - there are not as many pure C kites today as just one or two years ago - but not because they are not good, just because it is a smaller minority who want these nowadays