What's the point In using a 3/4 self inflating camping mats,

I don\'t understand!! Why use a 3/4 sleeping mat when it\'s not much different in wight from a full size one,, I don\'t dislike them at all I just don\'t see the point, The new 3/4 sleeping mat ?????????? https://www.gooutdoors.co.uk/15904969/oex-traverse-34-self-inflating-mat-15904969