Why not? No real reason other than a novelty and it's easier to get the dried-on mucus off in the morning or the rare occasion when I'm sick.

It's also easier to get popcorn kernels unstuck from my back of my throat when that happens and easier to extract tonsil stones without using my finger or a different oral tool.

Also, as I've replied to other comments, I've got a slightly higher mucus production than most people seem to naturally have. So it helps to not have to blow my nose as often.