There are a lot of e-mail systems out there with not very good spam filters. And spammers do change up their methods to get around filters. You might not notice

There are a lot of e-mail systems out there with not very good spam filters. And spammers do change up their methods to get around filters. You might not notice them, but people with less effective spam filters do get them. (And some people are dumb enough to read e-mails in their spam folder) It's always been an economic numbers game. You might send 1 million spams that costs you $100, but you might get $400 in return from whoever paid for the spam campaign. If you're running your own spam operations for your own "products", you get more profit, but the risk and difficulty is higher. I also have a theory that spies use spam as a form of steganography. If spam naturally contains a lot of variable information, and it comes from random places and is sent literally everywhere, it's not hard for a spy to receive an encoded message dropped into their mailbox without anyone even knowing what their e-mail address is.