My theory on them has more to do with handling and transport - the ones I have seen - either get moved around and used a lot (Easy to bang the air filter cover with a knee while carrying it) or truck mounted (Road Vibrations while in transport)
Might consider finding some of those older style spring type isolation dampeners to mount the whole generator to the truck - which can help with the road vibration thing (but won't do much for vibration from air flow while driving down the road).
That air filter base was not exactly the best design.. all that weight hanging from 2 bolts..