Comic book origin stories were all the rage at the start of the 21st century, and, as a general rule, their titles tended to be short and to the point. As in, "just the character's name and that's it" short and to the point.
Spider-Man. The Avengers. Wonder Woman.
There's no need to bog viewers down with flashy adjectives and wholly unnecessary verbs up front. For origin stories like Deadpool, the goal is to introduce the star. Besides, if that first flick goes well, there will be plenty of room for flowery, vaguely descriptive titles later in the franchise.
(Yeah, we're looking at you, Ghost Rider: Spirit of Vengeance.)