There are some other niche scopes that do this, but it doesn't seem common. There are also some dedicated devices (e.g. bode 100) which are designed to do only this.
I personally know the guy behind Cleverscope, which does turn a sig-gen+scope into a network/frequency response analyser (see
https://cleverscope.com/fra/ for info).
He was originally pitching his CS328A scope as a general purpose deep(ish)-memory PC based scope back when they were relatively rare and expensive, but is now much more useful (and marketable - the price for just the basic scope features isn't competitive anymore) as an instrument for specific jobs needing this analysis capability, which was added to the software after the initial design was done.
The unit I have has been extremely useful for measuring passives, transformers, resonant circuits, power supply gain/phase and general freq response stuff - it gets much more use than I expected, and I would completely agree about the "killer application" thing (though maybe not about the triviality of doing it well).
As for more general purpose scopes, I also have a RTB2004 with sig-gen, which has proven quite useful, but not nearly as good as it could be if the integration was better done (can copy scope waveforms into arb-gen memory, but arb depth/speed is limited, and there is no trigger sync facility). You can do some response analysis stuff using peak-hold FFT and freq sweeps on this scope, but it certainly isn't as good as if they'd written the code to do it properly!