"Taxation isn't about what you need"

In January 1986 the political comedy " Yes Prime Minister" featured an episode "The Smokescreen" in which The Prime Minister, Jim Hacker, favours abolishing smoking through heavy taxation but he runs into strong opposition from the tobacco lobby and the Treasury department.

The following exchange between the PM and his permanent secretary, Sir Humphrey, seemed especially worthy of reference:

Sir Humphrey: Taxation isn't about what you need.
Jim Hacker: Oh, what is it about?
Sir Humphrey: Prime Minister, the Treasury doesn't work out what they need to spend and then think how to raise the money.
Jim Hacker: What does it do?
Sir Humphrey: They pitch for as much as they think they can get away with and then think what to spend it on.