NVRAM is very important, you never needed it until your phone is totally bricked and your baseband is damaged showing only UNKNOWN.
If your baseband is damaged, RADIO (network)of your phone might not work. Your phone do not accept sim card. And when you go to settings, your SIM Card management is grayed out (If you have dual sim phone).
This is when you need to restore your NVRAM. You need MTK Droid Tools for you to be able to backup or restore your NVRAM.
To be able to restore or backup your NVRAM , you need to root your phone first. Then in MTK Droid Tools click in IMEI/NVRAM. And you can see the BACKUP and RESTORE process.