[kevinoid]

You can read about the specific reasons that driver versions were blocked on the Mozilla Wiki https://wiki.mozilla.org/Blocklisting/Blocked_Graphics_Drive... Most are due to the drivers causing crashes or security issues in Firefox.

I think a broader answer to your question is that most apps accept that if a driver causes a crash or security problem, it's not their problem and it's up to the user (and driver developer) to remediate it. Firefox has chosen to attempt software fallback to avoid the issues. There are obviously many trade-offs for good and ill with this approach.