People usually think that sign language was artificially created to help the deaf people. This is of course very wrong, but tells a lot about how society perceives abledness. In this case we could even talk about being deaf is a disability, but that's a topic for a other day.
Actually, sign language historically developed similarly to how spoken language developed. This means that even within one country, many different dialects are spoken. This can be easily seen for rather simple words - the word "Friday" for example can be vastly different in one city compared to the other.
I guess it also depends on what type of musician you are. If you come from traditional instruments and want to record some nice drum patterns or so it's a really nice tool. Otherwise you have to artificially add some random off timing (like ms) to recreate that natural feeling. I could imagine many people can also be more creative playing on an instrument (which a midi keyboard basically is), getting that haptic feedback instead if just clicking things together.