If I recall correctly, the Enforcer was rammed down the USAF's throat by Congressional supporters, some of whom were "military reformers" who thought that Western armed forces should look like Tass agency photos of Soviet forces, just smaller and less drunk, and others who were getting campaign dosh from the Enforcer's builders.
The point is that airpower that works in a permissive environment can be countered easily. If my adversary is coming after me with trainers armed with 7.62 and rockets, the 2S6 will merrily rip them limb from limb. It will have a much smaller lethal envelope against a proper fighter, which will bomb the 2S6 into a more harmless condition and then get on with the CAS job.