8. Why Didn't The Enterprise Just Send A Shuttle To Save Sulu?
This is the one entry on this list that will discuss a purely behind-the-scenes reason, as there is a seperate list for that. In the first season episode of The Original Series, The Enemy Within, Sulu is stranded on a planet where the temperature is dropping rapidly. If he remains there for much longer, he will surely die. However, they can't use the transporter to bring him up, as it's created an evil clone of Kirk.
Not only is a shuttle not sent to save him, but it is never even discussed as an option. There is a simple reason for this - they didn't have a shuttle to work with yet.
While the Enterprise had been designed by Matt Jefferies to have a shuttle bay, Desilu studios were not about to commission building a shuttle on the off-chance that it would be used in the show. Therefore, when it came to this episode, using the shuttle simply wasn't an option. Thankfully, Gene Roddenberry found a way around this several episodes later. He specifically wrote scenes based on a shuttle so that the prop department would have to build at least the shell of one - adding an excellent element to the show, and condemning poor Sulu to always having been forgotten on that damn planet.