Maybe because it's discoverability is bad. I've been looking for something to control screen brightness because I wanted to give Linux another shot, so this random post was a lucky find.

If I look for this topic on ddg I either find a Ubuntu wiki entry(not really relevant to me on suse with KDE), the arch Wiki which focuses solely on technical details and clis. The first ten articles are clis, a lot of them truly strange ones like writing magic numbers into random system files.

Not a single mention of gddc tho, and the manpage is not a very good advertisement either...