Because jasper-compiler-jdt.jar is the Eclipse compiler. We shouldn't duplicate code.
I agree that it shouldn't be a hard dependency though. There should probably be an alternative dependency on an appropriate virtual package. Moreover ecj-bootstrap should really be used as a bootstrap compiler only. From the package description: "This bootstrap version should be used for uploading initial versions of packages which are a dependency of Eclipse and build with ECJ." Either the decsription should be fixed or the package renamed, or replaced with something more suitable.
