Part of the issue is they have been patented to the hilt by parties like S3. It hasn't been an issue in video games because companies just agree to implement other S3 apis in return for a patent license, but in cases like this that obviously isn't an option.

https://en.wikipedia.org/wiki/S3_Texture_Compression

It has been an obstacle for open source drivers too, but luckily this specific patent expired.