Vic83,
Very good question. 1/4 tone scales are important for much ethnic music, especially around the mediteranian area, such as the middle east, greece, eastern europe, turkey and others. Huge amount of these groups of people immigrated to the USA and became part of it. Music is very strong with them. I would say that most people who buy GEM arranger keyboards in the US, will also buy the oriental kit with it. I know some stores that sells only these kind of keyboards.
Because of this large ethnic oriental music influence on our culture, nowadays, many of the modern music especially by african american musicians utilize sometimes quarter tones in their music.
Furthermore, many of the movies that are produced in hollywood utilize quarter tone music in the background to give you the feel of eeriness, strangeness and sometimes uncomfort.
So it is no longer an option if you want to be musician for everything. You must have all the tools, all the technology and a GEM keyboard!