That bothered me for a while until I figured it out. After a while, I learned that underspent projects are your opportunity to learn new things, mentor junior

That bothered me for a while until I figured it out. After a while, I learned that underspent projects are your opportunity to learn new things, mentor junior people, and provide cushion to people waiting for their next projects. The only thing I ever got reprimanded for was not spending my money - there are much harder problems to solve than that.