Configure fstab delay_root parameter with 5 or 0 seconds?

In the fstab configuration is the parameter delay_root. My system (Onion Omega2) has this configured as 5 seconds but on the internet I find many other devices where it is configured as 0 seconds.

The OpenWrt wiki is very short in the explanation of this parameter:
"wait X seconds before trying to mount root devices on boot"

I have an application where the user will insert and remove the USB stick often. For a good user experience I would like to create a quick response on the user inserting the USB drive.

Why was this delay parameter created? It feels weird to introduce a delay.
Would the system respond faster when I change this setting to 0 seconds?
What are possible negative effects of reducing this delay?

Just to be sure I understand this correctly: The USB stick with the root filesystem will be changed often? Or rather a USB stick with just data (photos, music, videos) on it?

I start to sense my mistake....

The usb drive contains only data. So this setting has no effect then?

Will my device with permanent flash memory boot faster with the delay_root set to 0 seconds?