If you work for a studio or with people that all use pro tools it would benefit you to be able to burn your project files and be able to load them straight up. Otherwise you'd be exporting wavs and you also wouldn't get any plug in settings etc.
Its funny actually, i've been using pro tools for about 5 years now, and am making the switch to cubase because everyone i work with is using cubase. Prior all the studios i was taking my mixes to were working on pro tools hd systems.
Being able to transfer my project files to my colleages is a reason i would use a particular program for a project.