It is not compulsory to use any or all the options in Premiere if they dont suit you or are not to your liking.
Off lining a clip with the abilty to clear it from the drive is a great option. (Which I use a lot)
Some editors use it when they are using a place holder clip.
Some editors might use it when they dont want Premiere to go searching for a clip..eg on a temp drive.
Thanks for the info.