They study the stats, and sculpt their messages accordingly. According to an analysis by CipherTrust, clickthough rates on spam vary enormously, with porn leading the charge.
– Porn 5.6%
– Pharmaceuticals 0.02%
– Rolex watches 0.0075%
Of course, that is most of what you see too, proving spammers know their business. Frankly, I know why Rolexes are so low – they cost a mint to fix!