Ashley,
Point 1) There are many cases where a game works perfectly at high FPS and then fails casastrophically at low FPS. Delta time is fantastic, and its great to ensure stuff stays the same speed despite FPS, BUT this very solution to one problem makes objects fall through floors and otherwise completely miss critical collisions with objects, enemies etc etc at much lower FPS. The ability to cap frame-rate (at least while testing) would allow game makers to easily make sure the game works great across the board..even on weak devices.
Point 2) It seems to me it might be simple to allow the game to detect the power of the device its on and adapt the fps accordingly, as in: If FPS of title screen is < X, then cap FPS at 30, if FPS of titlescreen is greater that 50, then remove FPS cap....so perhaps there is no good reason to assume that capping the FPS will degrade anyones experience, in fact, only guarantee best experience across all platforms. (because we could turn off the cap either before making the build for high end platforms, or have the game turn off the cap at run-time if running on a powerful device.)
cheers,
Mike