Is it necessary to turn on Nikon D5 100 exposure delay mode? When shooting what scene, the effect is obvious?

Exposure delay is a measure to prevent machine vibration, similar to the pre-lift of reflector.

You can open the shutter when it is slow, such as shooting at night.

In fact, there are many ways to prevent the vibration of the machine, such as taking a selfie for two seconds and releasing the cable to reduce the vibration.

These are all useful on the shelf, but they are useless to hold.