They probably don't include many "modern" styles because of people like me. I don't care if they are there, but I won't be using them and would prefer they use the space for up-to-date Country, Ballad, Blues or Rock styles.
Oh yes, and it's people like me who buy the blasted things.
If you listen to a "Country" radio station now, there is very little traditional country music on it. Oh sure, they put a little steel guitar in the background to "brand" it, but most of the modern country songs are slightly reworked rock or pop style songs. The days of 3 chords and the truth are pretty much past. Michael Buble and Blake Shelton both released powerful versions of "Home". They were quite similar in sound and feeling.
I mention Country, Rock, Blues and Pop, because I prefer songs with a melody and chord structure of some sort, yet don't want to be mired in 100% oldies.
My very limited concept of Hip-hop and other modern styles is that the emphasis is on the beat rather than the melody or structure. That is almost certainly an over-simplified statement though! However, it would seem that a talented style-maker could create and market a catalog of modern styles. If the market for them is really that strong, he could make a lot of money. I know, after the initial wave of sales everyone would copy and re-distribute them, but by then the current market would have changed and the style-maker could create "today's" crop of styles. I suppose Yamaha is the industry leader in volume, so that would be a good brand to start with.
Squeak, maybe you could make this into a lucrative business, or at least a sideline.
Back in the late 70's, early 80's, a friend of mine and I once started a small business writing styles. We sold a few locally, many of them simply drum patterns for Yamaha and Alesis machines. The problem then with arranger styles was the limited memory available on the keyboards. There was only room for one or two user styles at a time, and loading new ones was slow. All that has changed now of course.
Just rambling. . .
DonM