The answer is: music schools. We don't see this in the west so much, but Yamaha run the worlds largest networks of music schools, predominantly in Asia.
The DX21, DX100, DX27, FB01, TX81Z .. product range .. is designed to cover the following use cases: music schools, karaoke bars, normal bars, and hobbyist musicians. In fact, Yamaha's biggest FM-based products (in terms of sales generated) is the karaoke market, where the more 'sophisticated' synths would be used by karaoke artists to create the MIDI files that then get shipped off to be 'played back' on the karoake-friendly devices, such as TG-series.
The DX21, DX100, DX27, FB01, TX81Z .. product range .. is designed to cover the following use cases: music schools, karaoke bars, normal bars, and hobbyist musicians. In fact, Yamaha's biggest FM-based products (in terms of sales generated) is the karaoke market, where the more 'sophisticated' synths would be used by karaoke artists to create the MIDI files that then get shipped off to be 'played back' on the karoake-friendly devices, such as TG-series.