I'm absolutely guilty of this. I'm a software engineer, and I feel proud of having worked on products that millions of people use. Steve Jobs's challenge to "put a dent in the universe" is axiomatic for many of us.
Yet I know that in other countries (e.g., Japan) there is a belief that any job, no matter how humble, is worth doing well and that passion for excellence is a virtue inside us and is not conditional on the perceived pecking order of the job.
If we had such an attitude, maybe it would be easier to feel fulfilled--if you're holding out for changing the world before you can be happy, you're (statistically) going to die miserable. On the other hand, maybe a culture in which we give 110% to meaningless jobs is just another chain for the rich and powerful to keep us productive.
I honestly don't know.