Revolutions whether or not they led to war are very effective!
The American Revolution: Well, look at the U.S. now!
Cuban Revolution: Cuba is now an independent country.
Civil Rights movement: The Revolution that gave African-Americans equal rights.
Woman's Suffrage: A revolution that gave woman equal rights.
Upper Canada Rebellion: The Canadian Revolt against the British. Well, now look at Canada.
I could go on. To get my point across, without revolutions... Nothing would get done. Let's all remember, there is a difference between Revolutions and Revolutionary Wars.
Revolutions happen not only in the physical revolt of the masses sense, but also in ways of thinking and in knowledge. All these types of revolution are the only way to shake everyone out of the normal way and get them to accept and understand the new ways of thinking or knowledge. People are dogmatic in their beliefs and often the only way to get the message across is forcefully, as unpalatable as that may be for a civilized society.
I believe they are import for changing society in positive more than negative ways. This is because if enacted in a just/peaceful way, Revolutions can remove previously instated systems that may be harmful to society. Of course Revolutions can bring about added corruption, but the fact is they are meant to wipe away beliefs developed on a corrupt base. They establish a new beginning in societies, that overtime fix the weaknesses brought about through venturing into new systems. For example, America has undergone many Revolutions regarding women rights, and although success at perfecting the equality women have today has never been easy, it goes to show that the Revolutions marked were turning points in how women should be treated.
Revolutions never prove to be effective it takes a very long time for a revolution to be considered effective. People end up asking for too much and it's complicated to meet all those needs at once. Revolutions also sometimes end up in conditions similar to before the revolt such as the American and French revolution. If anything revolution still continues because people are still asking for similar things as those before them.
The question is not wether they're good but effective, and no they are not. You can point towards large ones such as US/Haitian/Cuban, they're easy to remember because something came from them. People tend to forget how effective a normal revolution can be. If you need examples look at British Empires history, countless of people attempted to get Britain out of their people land, did it ever really work? A great example would be the Sepoy Rebellion