Well, what should they be doing then? And Qui Gon served the senate himself - he was the first jedi we see go on a mission ordered by the supreme chancellor! The only thing was, that due to his maverick ways he would never make it on to the council as he was unorthodox from time to time - nothing to do with serving the Senate. The Jedi stand for democracy. If they were an independant order then they wouldn't be adhereing to the rules of the democracy. They would do what they thought was right and what they wanted. It would go against democracy. The only thing they can do and the best thing they can do is serve a senate which expresses the views of the galaxy. The problem occurs when the senate becomes corrupted - mainly through the plotting of the Sith, and the Jedi end up working for the wrong guys. Then they have to destroy the Sith and take out the corruption and go back to serving a just and honourable senate. Thats something they managed to achieve for a 1000yrs before the Sith re-ermged and took it away from them. They would have destroyed the Sith and got it back sooner had it not been for Anakin.