I'm thinking they just don't know how to bind custom controls. Granted I'm not going to bother setting up again to check if it's been recently broken...but:
Last time I tried I managed to bind a PS3 Controller to starmade and had it work just fine with both astro and ship controls. This required some BT stack hack magic to make PS3 Controller connect to windows, but modern multi-axis controls shouldn't need that kinda hacking...
Side note: I Also got a wii-mote working as starmade controller in the same year so...
Will. Way. It could probably be made easier with a half-dozen scripts, or if starmade recognized the full USB HID protocols natively.