Mario & Luigi Rom Hacking: Why hasn't it gone anywhere?

The Mario & Luigi games, (since this is in the ds section, pit and bis) would be perfect games for rom hacking! Imagine custom enemies, items, story, areas, e.t.c. I know there are some simple tools, but I'm just wondering how easy it would be to do create a proper application to create rom hacks. m64ds, mkds, nsmb and others are large in terms of rom hacks with mpds even being in the mix now, so how come the M&L games haven't been explored much in terms of rom hacking?

I know very little...

Mario & Luigi Rom Hacking: Why hasn't it gone anywhere?