Why don't citizens have more power?

I don't understand why we leave all of our decisions up to a few select men when we're capable of making some of these decisions ourselves. If the whole process is supposed to be for the people, why don't people have more direct influence over issues?

Just two examples I'll give:

Taxes: Why don't we have direct control over what they're actually spent on? If we're going to pay taxes why shouldn't we have more influence on what they're going to be used for.

War: How is it we have no say over whether or not our own nation goes to war? If the common people are going to have to pay the ultimate sacrifice in wartime, shouldn't they decide whether or not it's worth it to start a war?

any responses that will help me understand why we the people don't control more would be appreciated.