Yeah, it has no logic, that's a fact, altough how Coriko said, traders can just kill and continue in speed 349-330 for next half hour... which is.. wrong. Also some capships (GB...and the especially missle GB vs Fighter class) would be a bit too ultimate if you can't engage their engines again. So. I'm not sure, we cold prefer either realism or leave it how it is.
I buy things I don't want to make an impression on people I don't like.