Well, you got to think. If you were awarded points for taking over CD positions, you'd have people who just wanted a whole bunch of points, thus just join a whole bunch of CD games. They wouldn't be forced to do a good job, etc etc etc.
I think the system is acceptable the way it is. The price you pay is a good example of risk vs. reward. You pay high for a good position, and low for a losing position. The more you invest, the more you stand to gain.
Furthermore, when a country is in a losing position (that is, everyone attacking stands to gain nothing by leaving it alone) it's best to have it just die. I mean, sure, it's always nice to be the monkey wrench, but seriously, when you're probably going to die anyway, why invest/waste/bother with those extra 5/6 points?