Every film ever made will have had to make great sacrifices over the course of its production in order to keep costs down. Ideas and grand sequences that were planned at the screenplay stage or even storyboarded often end up being too costly or too distracting from the rest of the film and are ultimately cut out.
In other cases, films are trimmed for run-time or flow extremely late, when scenes have been filmed, sub-plots established and the film is heading for the end of production. Most cuts are made without concern: they are simple choices that trim out flabby moments or tighten others up, but there are some that seem utterly baffling when the evidence comes to light.
Sometimes directors and editors remove key or entertaining sequences that would have actually improved the final cut of the film, and it's inevitably frustrating - particularly when they then show up as part of the Special Features on the blu-ray. And you'll be surprised by the size and quality of some of the films that could have been improved...
10. The Avengers - Captain America Adjusts To Modern America
Instead of showing Iron Man spending half an hour fixing the Helicarrier, how about making room for just three minutes of this beautiful, tragedy tinged sequence.
This adjustment period was sorely missing from The Avengers, and seeing that it was actually filmed and ultimately jettisoned (presumably for pacing and for the fact that it's utterly devastating) is even more ludicrous. Seeing Steve struggling without something to define and distract him is the stuff that pathos is made of, and it actually gives Chris Evans more to do than just flexing his muscles.
It's now pretty much universally heralded by Marvel fans as the most bafflign cut scene ever, and it's not exactly hard to se why.