When you're implementing macros anyway, why not go all-out and just embrace LISP? You've got to make a pretty convincing argument to make me agree that whatever language implementing macros is better than LISP. From what I gather, the main issue that makes people not want to use a LISP dialect is library support, and no new language is going to have that.
It's not an issue of libraries - you're clearly right that new languages are likely to have less impressive libraries.
It's partly a matter of syntax - frankly, I can't deal with Lisp's syntactic minimalism (my problem, maybe, but there's a lot of other people like me). So there's an immediate argument for adding at least Lisp-like macros to a syntactically rich language (a task which, historically, has proved very difficult).
It's also, as suggested by henning, because there is more to meta-programming than just Lisp-esque macros.
Not all macro systems are Lisp macro systems?
Languages may have interesting features other than macro systems?
Library support may be cleverly piggybacked in from an existing language? (see C -> C++)
