Exactly! You actually CAN have 50 people finish something 50x faster, but it takes a shitload of planning, and that equals time and money no company I have ever worked for, or even known of, would allocate to something that isn't generating immediate income.
Take the Hoover Dam for example: Dsigned over 3 ish years and built in 5, at a time when nothing that huge had ever been made before, at less than a billion in today money, and 2 years ahead of schedule. It's 90 years old.