>>536596745
Lot of reasons, the tl;dr is laziness mostly. Without HAR a lot of people's super special multi-armed futanari half-demon naga/centaur hybrids had no easy framework with which to add body parts that were capable of certain functions, and the C# part of HAR let the .xml only masses finally have an easy way to go about it. Nowadays there is basically nothing* able to be achieved by HAR that some sort of framework for Biotech doesn't also cover, but modders are lazy and don't want to redo things. Biotech also requires them to rewrite parts of the HAR into genetypes, so they're also unwilling. Basically HAR reduces the coding bit of making your OC alien into .xml only. Biotech frameworks now exist to do the same, but see aforementioned laziness.

*The way Biotech works by genes and not entirely new races means that some of the HAR bits are wonky. I don't think any framework for Biotech exists as of right know that lets people easily change the "Human" part of a pawn's info, they're always human xenotypes. This can cause issues with apparel where HAR has a system for restricting what apparel can and can't be worn.