My GoPro can record 4k@30fps. A 20-25min video is 5+gb. The newer GoPros will do 8k@60fps i believe, maybe only 30fps. That will take up a lot more space.
The cards have to be the higher speed cards to be able to record those resolutions, but if I were a person that recorded a lot of stuff, having a card that large would be nice for a day long session.