Every Game Master knows that things happen in a game that aren’t planned for. When these things occur there is often a mad scramble on the part of the Game Master to try and make sense of it in an intelligent and well-thought out manner so the story can proceed without undo disruption. This is when the elements of time and distance can be harnessed to help slow things down enough to allow the Game Master a chance to get some planning done before the players go careening too far and too fast.
The modern reality that we all suffer through between game sessions has for the most part made us immune to time and distance. We can fly great distances quickly and our communications around the globe are nearly instantaneous. But in Dungeons & Dragons things are not that easy, nor should they be. Look at how long Frodo and those other hobbits were off on their adventure, and how far they travelled. These things are rightly the stuff of epics by the mere fact that it is an epic feat to go that far and be away from home for that long. That is how Dungeons & Dragons is structured. It takes a while for news to travel, and for people to get from one place to another. Physical endeavors also take awhile. And if you are trying to invent a primitive helicopter? Oh my, that is going to take some time too.
Of course there are ways to allow players to speed things up and get places faster. The trick is that the Game Master has to allow these things to be available as options. Not every option should be available nor should they be available all of the time. Remember that the Game Master still has to be able to plot out events and activities well in advance of the players showing up to that point in the story or else the entire thing reeks of a cheap video game. Can the players build or buy a spelljammer to make their travels faster? Possibly. Can they develop a magical means of communicating between people over great distances quickly. Maybe. Will such shortcuts make the game go faster and take away from some of the fun? Absolutely. There is an advantage to waiting. If you go too fast you miss a great deal of scheming. And a game without scheming is just a waste of a good time.