The enterprise is a story vessel. Nothing makes sense in a practical sense but everything can be used as a setup for an interesting story. Every device is a plot device.

The transporter can beam down just the combination of characters needed for a story to a planet that's ideal for the story and then it will fail to beam them up because of some weird radiation. The engineering department will need to punch random buttons to fix it exactly as long the story on the planet needs to conclude.

The holodeck is the most versatile plot device and Q the most versatile joker.