Software development is complicated, just because something works in a particular use case, doesn't necessarily mean it's ready for release. In terms of the RPH's ability to hook the in-game sirens, I looked into it and it's a little more complicated than slapping on a UI and some patterns (not that those are easy tasks).
TL;DR Programming can be difficult and time consuming, things like ELS or LSPDFR have the added challenge of being hobby projects of others so they'll take a fair amount of time.