Well, that is how it works in a sense. Higher level drives let you travel further without any noticeable increase in energy used that I've observed. But I can see why they did the distance limitation as a gameplay thing -- otherwise, getting to the core would be a no-brainer. Just get max energy stores, blow it all on the trip to the core in one or two shots, and then get a free trip back home when your ship goes boom.
I hate arbitrary limitations in a game. Especially when they exist to cover poor design.
Dammit, remember the good ol' days (tm) when we had games like Frogger where if you screwed up, you got squashed? Or Design-a-saurus where if you didn't design yourself properly, you got eated?
Why do so many "kiddie" games these days think that failure is taboo?
[edit] I'm sorry, I skipped a few points there...I'm referring to the non-existant death penalty in the space stage.
Because its taboo for kids to fail these days. Just look at all the schools that have abolished the "F" grade...