As +Theodore Ts'o
said last year, mutt makes it trivial to see the phishing attempts and other "fun" emails I get all the time.
Combined with the fact that it enables me to handle with ease huge volumes of email that make people who use gui email clients cry, is also of course the main reason why I use it.
Heck, I even use mutt with some gmail accounts, it handles them with no problems at all and enables you to see threads of patches which gmail has no way at all to show in the web view.
Highly recommended for anyone who relies on email for their work (which these days, is almost everyone...)