You ever TRY to hook up any other MIDI gear to a Yamaha? Ever want a module to play the drums, but use the internal sounds for SOME parts? You ever want to control the Yamaha's arranger functions (Variations and fills, In/Outs etc.) from another arranger or a remote keyboard (only way you'll ever get to play a 76 Yamaha arranger!)...?

It's easy to not find limitations, if you don't look for them (because you don't need them)...