Space research is an expensive business. Once a space-based instrument is proposed, researchers want to get as much value as possible from it. The proposed satellite quickly grows in instruments and capabilities. Expensive, radiation-hardened components must be used. The expense places satellite instrument platforms out of reach of most research budgets.
Source:
https://phys.org/news/2020-03-halosat-galactic-x-ray-shoestring.html