You live in the suburbs of London, and decide to have a late night out to central, for the purpose of this example, say a nightclub that closes at 3am. How are you expected to get home after that. Taxis cost a bomb, taking the tube is easy and convenient. And to me, one of the safest ways to travel. So it is ludicrous that the tubes arent 24hr services.
Ok currently the tubes in and around London stop running at around 12/1am. It would be better for everyone to have the tubes running for 24hrs. Even if it some particularly busy lines and on some evenings, i.e the central line and friday and saturdays.