It's too painful for people to check their facts before declaring mainframes dead or something IBM is leaving. As you said, they're incredibly profitable. Same thing happened with OpenVMS, which turned out much profit for HP despite little investment. Next they'll be telling us Group Bull, Unisys, and Fujitsu are similarly scraping by in the mainframe business. And NonStop and IBM i are on verge of cancellation. And blah blah blah.

I'm sure we'll be hearing the same crap in a decade while said crap is posted via a service that imtegrates with a COBOL app on a mainframe. ;)