Reason not in the repos, from the home page:There is no goal to make the most possible software available, KaOS will stay limited in size of the repositories, and will work on......
No-one ever mentioned autokey, so certainly not a widely used app here, not one that will be replacing current available packages. Repos are at their maximum size, anything added will mean removing something else.
But also, read why pacman was chosen for this distro (and will guide you how to build autokey):
And you are in luck, there already is a PKGUILD available for it: