You've got the causation backwards. ASTM is an engineering organization like ISO. They develop industry-consensus standards, just like ISO. Their codes didn't get adopted as the standard because they lobbied for them (do you even have any evidence ASTM lobbied to get its standards adopted?). They got adopted because they were the industry standards.
It's like if a law stated that certain government contractors must use ADA or C. They'd refer to the ISO standards for those languages, but nobody could reasonably come along after the fact and say they did so because of lobbying by ISO!
Even if ASTM itself doesn't directly lobby, it's ... delightfully or frighteningly charming, take your pick, that the naive view of an industry organisation not being utilised by its members for their direct benefit through rules-setting wouldn't find itself used to do so. Directly, indirectly, overtly, or otherwise.
It's like if a law stated that certain government contractors must use ADA or C. They'd refer to the ISO standards for those languages, but nobody could reasonably come along after the fact and say they did so because of lobbying by ISO!