For the same reason that you pay for train maintenance despite probably having a car (At least in places with nationalized trains).
Also are you comparing being homeless (and risking death from disease, and the winter months in the process) to the simple inconvenience of taxes? I'm sorry, I cannot discuss any longer with someone who is willing to consider things so loosely and callously.
Okay. United Kingdom has 34.4% of tax to GDP ratio. That means that out of 5 working days, almost 2 days are given to the state. I would not consider working 2 days a week for the government a "simple inconvenience".
Also are you comparing being homeless (and risking death from disease, and the winter months in the process) to the simple inconvenience of taxes? I'm sorry, I cannot discuss any longer with someone who is willing to consider things so loosely and callously.