No, the main reason to have damage ratings is so that people don't confuse a rocket that can take out a motorcycle wheel with one that can one-shot a tank, or a skyscraper, or even a battleship, understand the difference between 4mm and .50 cal, muskets and gauss cannons, or use a weapon that could destroy a city (or planet!) against a starship only a few hundred meters long while only causing moderate damage instead of vaporizing it completely.
The purpose of DR isn't to create a game system that can be played, it's to give an understanding of how powerful different weapons are in the RP, and to a lesser extent, how well the setting's ultra-tech vehicles and their barrier screens can stand up to them, in comparison to more conventional targets. It's for comparisons and conveying unintuitive information, like that the NSP is far more powerful than any modern-day sidearm.