I posted it to ask English translation for my Japanese sentences. But of course I’m happy to answer your questions. 😃
1. Japan is humid, especially during summer, so heads tend to be muggy and sweaty. Japanese people take a bath almost every day since right after we are born. You could imagine it will become your habit to take a bath and wash your hair if you start that at so young age. Then, since it’s humid, if you use a hairdryer, it’s faster to dry your hair. There are hairdryers that have special functions good for your hair, too. Come to think of it, my brother never use a hairdryer for his short hair. 😅
2.From my experiences, I believe Subuta usually has pineapples. Personally I think most Japanese like both pineapple and takenoko. Each has different texture, flavor, taste.
3. At a high-end restaurants, I wouldn’t recommend you pour remained sauce over your rice but at home, it will be totally OK. Maybe at a casual restaurant, it’s OK, too. Thank you for trying to be polite at a restaurant. Nobody will criticize you when you pour sauce over your rice. We have a dish called ochazuke which I believe you already know. Also, when you eat gyu-don, Oyakodon, etc., sauce is already poured over rice. Don’t worry and enjoy your subuta! 😃