Also a huge advantage is the mobility of a scooter over a bike. With a scooter you are more flexible to changes in your day. Did a friend just message you during lunch to meet up for drinks in a different part of town? No probs, just take the scooter on the tube after work. Did the weather just change drastically? No probs, can quickly change to a different way of commute and the scooter doesn't feel like a huge showstopper whereas with a bike it all becomes really really complicated.

Bicycles in big cities are too inflexible. If all you want is to commute like a sheep from home to work and back to home every day then a bicyle is a great inexpensive and green choice, in every other case it's a problem. Unless of course you are in a small village, where a possible change of plans will still result in a short ride. In London this is not possible. If I was to meet friends spontaneously outside my daily commute area then it would be impossible with a bicycle.