I don't think it's the "majority" of buttons sets but rather the newest sets that haven't been included. External linking had become a major issue that needed to be addressed. We have been working on setting up a new system for the graphics for quite some time now (with bumps and glitches along the way) and thus, things have been put on hold for now.
Hopefully we'll get something usable as well as reliable in the near future. (there IS something in the works.
)