In China at least, toilet paper wasn’t soluable for a long time and sewer plumbing wasn’t up to standard, so you used the waste basket for your TP. You would also bring your own TP to public bathrooms and they had no idea if your TP was soluable or not (lots of cheaper kinds aren’t). These days, toilet paper is universally soluable and plumbing is much better, you can totally flush it (and I always do when I’m there) but so many people grew up being told not to that they still have and use waste baskets.