Why would you bring your own chop sticks? It's not like the ones at restaurants are super dirty.

It's because Muppo has a bad habit, and very bad luck, with splitting the wooden chopsticks as well as breaking them with her immense strength.

And, so...so close. Almost did it Muppo, but alas misfortunate strikes again.
I can also see the Poi Poi sticker so I assume this is Poidachi's Ramen shop and that hand is hers.

A lot of ramen places use disposables, so maybe Muppo wants to be eco-friendly?

Hmm.. I think it's more like eco-friendly thing.

Also, this was to avoid badly split chopsticks. Damn it,Muppo - leaving them behind is as bad as tossing disposables away.

I think it is a combination of all ideas. You have your own, so you don't have any fear of unclean chopsticks, you do not worry about breaking the weak wooden ones. And probably you are cleaner too. All of this, of course, if you do not forget them in the shop.