Platforming in a first-person perspective could work if done well (Portal and Mirror's Edge come to mind), but there's a fine line between being good and being unplayable, and part of that comes down to the game's focus. In Mirror's Edge, Portal, and Mario platformers, the goal is ostensibly to reach the end of the level, but Mario games have power-ups, enemies on every plane, shiny things to grab, and a lot of other things that would simply be too distracting if they were to be retooled for a first-person experience.