I think we, ambitious, studious, people, try very hard (and earnestly believe) in the capacity for our jobs to be fulfilling. After all, there are tons of Emotionally Fulfilled people out there doing jobs that seem rather fantastic. Solving big problems. Making lots of high level decisions. Etc.
But over time, most of us, as a rule, simply see our jobs for what they are, and become less engaged with them. We're "on the clock" and that's about it. We want to be comfortable. We want to be paid for it. Etc.