Because I want it to be smaller. Full size XLR are great for compability, but they'll make the camera bigger - maybe the same size, like a tiny smaller than the C100 Mk II. And I don't want to deal with an adapter such as the MA400 which came with the XC15 (that I've owned and after a while I've just gave up on using it).
If Canon decides to put full size XLR on the camera and make it bigger, that's a deal breaker for me. I'm already investing in a C300 Mk III (will be purchasing next week, can't wait) and I'll want a really smaller camera than the C100 Mk II. If this camera is not the one, I'll probably get a Komodo or just stick with my Pocket 6K (although I hate to deal with its ergonomics)