I don't think that's the case at all. Most good stories ebb and flow. It's important to give the viewer a chance to relax and build up tension before another exciting scene. But you're right, "Crank" is one of those movies that puts the peddle to the metal and doesn't let off. There is of course merit to that type of story telling as well.

Ebb and flow doesn't necessarily mean dead time. Gravity had plenty of changes in pace, yet I don't think it had a single pee break in it.

Well even in the screenshots it says you can go pee in the first few minutes of X-Men because it is "just silent exposition".

Now I haven't seen the movie, but that doesn't sound unimportant...

Sofia Coppola, on the other hand, makes entire movies that you can spend in the toilet