So 'blame the person who has less for them having less' is your answer in a nutshell.
Let's take a different approach then. A and B are identical twin footballers and work equally hard. Both are drafted to the big leagues. On the day before signing his contract, B gets hit by a drunk driver, and suffers career-ending injuries.
What's the argument now for why A "deserves" £3m a year and B "deserves" £30k?