I have a Casio CZ-5000, the 61 key version with sequencer. It’s well made but given its age I’m not sure I’d want to take that to a gig either.
That you can buy them on ebay all day long for less than most cheap synths costs new argues against it being viable.
Edit: But also, the CZ was generally more comparable to lower-end DX synths, like the DX27 or DX9. It was a budget synth in its day, while the DX7 was the pinnacle of digital synthesis for at least a year or two after release, everyone had to have one.
There's also a "Always wanted this, can finally afford it now that I'm rich" niche for the high-end remakes from Korg and occasionally Moog etc.
There isn't a huge "Bought this forty years ago because I couldn't afford anything better and would quite like a modern remake" segment.
Casio do still make pianos and Casiotone keys which include samples and some CZ and VZ series sounds. (I don't know if they're sampled or DSP.)