Rose gave him a chuckle and nodded. "Fine by me." she said happily. "Mum is a Muggleborn, so it's always been encouraged for us to keep contact with the Muggle way of doing things, including transportation." she told him proudly. "Really, what if you get hurt and you can't Apparate, or what if for some reason you can't make a mental image of where you want to go?" There were many reasons why someone would need the Tube to get somewhere.