I doubt I'm incorrect. There were 46 billion robocalls in 2020. That would be a $2.3 billion operating cost. Make it 10 cents and its 4.6 billion. Robocallers are not making 2-5 billion per year scamming people.
Or maybe this issue couldn’t be solved unilaterally, where one carrier could offer much better spam protection as a competitive advantage, and the industry is too decrepit for group effort that doesn’t have direct implications on their bottom line.