You might also think of it as a means of validating your bid and cost database. The better the documentation of your hours spent and the associated earned value, the better your chances of making money or knowing how much money you will lose when you "buy" in.
If you're off by 10% on estimating your hours, that could be half or all of your margin. While this is often made up by uncompensated overtime, the less you have to exercise that option, everyone will be happier and more productive.
Obviously, the planning aspect must be followed up by the bookkeepping; there's no much point in doing the planning if you never find out if your plan was actually on the mark or not. The earned value aspect is tough to thing to instill, but long-term benefit is an better understanding of where every hour of work goes. Additionally, it can provide you a better picture of program progress as well as potentially giving you an earlier indication of trouble.
This means that your tasks need to be segmented into small enough "chunks" with clearly defined products so that problems with schedule or productivity are readily apparent.
TTFN