not necessarily to use the paper for anything yourself, you'll probably only rarely have a use for blank paper, which is why people don't typically carry it around with them - the point is that if anybody around you ever needs a blank piece of paper but doesn't have one (for that reason), you will, and it's a small thing but i think there's something really nice in being able to help people like that. if you carry a laptop around already you can probably chuck some paper in with it - paper and laptop tend to be about the same size.

there are other things you can do this with - somebody will always need a pen or a bandaid or a charging cable or ibuprofen - and i recommend carrying those things too but blank paper is a niche i've accidentally found as something that very few people ever have on-hand. also it's lightweight and ubiquitous so as far as carrying things go it's an easy one to start with.

*or whatever the equivalent common paper size is where you are