Why do citizens want their government to be financially responsible?

Which country's citizens are you asking about. Please be precise when you ask questions, the people answering them come form all over the world.

However in general, in a capitalistic democracy, the government raises revenue by taxing the earnings of its citizens.

Thus the financial prudence of the government directly affects the finances of its citizens and indeed the level of public services provided to them.

If a government spends beyond its means the consequences for the country are similar to those that would aply to an individual doing the same thing.