When travelling it’s always a good idea to learn the bathroom habits of the country you are about to visit. It should never be taken for granted that things are the way they are here, all over the world. That could be a drastic mistake, especially if you were to visit somewhere like Poland.
A lot of countries don’t offer toilet paper in public restroom facilities so it’s a good thing to bring your own. You should also know where you might encounter someone that comes in and starts cleaning while you are still in the bathroom! That would eliminate a very awkward encounter, maybe.
Cuba doesn't have the type of money needed to put toilet paper in all public areas. It's best that you carry your own with you to be safe.