Spitting has become socially unacceptable in the US. This is due to large scale "anti-spitting" campaigns in the early 1900. In the 19th century when spittoons

Spitting has become socially unacceptable in the US. This is due to large scale "anti-spitting" campaigns in the early 1900. In the 19th century when spittoons were a thing in the US, TB ran rampant. There's also the widespread antibiotic use. The widespread prescription of Doxycycline for everything inadvertently does a lot.