Once you’ve crafted the necessary parts and built your elevator, all you need to do is press a button to ascend or descend. No need to climb up mile-long ladders, either. This is a big deal because it takes out the risk of dying when making long drops (hopefully) into a body of water.
The Elevator Mod fixes this oversight by adding a number of new blocks to the game which allow the player to craft fully functional elevators which go up and down like any normal lift. Even then, you would get a machine which only pushed you upward – it wouldn’t work the same way to descend, wouldn’t work at all, really. If you were working with only the standard blocks included in Minecraft, it would take hours to build a functioning elevator.