From experience I know that if your email address is a proper name, or word, you get more email than if your address is random letters and numbers.
My proper email address is the very registration number of my very first motor vehicle and gets no spam whatsover.
Of course, I don't use it for 'rubbish' sites, I have other email addresses for those.
But Ac is quite correct in saying that bots are used to generate literally millions of emails addresses in the hope they get a few right - after all, email is free.