If you're asking why the leaked "CFW" isn't compatible with the New 3DS, there are a number of reasons: you can't downgrade the N3DS to 4.x, the CFW doesn't work on anything higher than 4.5 (even on the old 3DSes), and nobody is working on updating this CFW that we know of, publicly (there are multiple private projects going on, but none of us here know if any of them will ever be released). Other reasons include the exploit used to launch this CFW was patched completely by 7.x, and from what I understand, the N3DS has an additional layer of security on the ARM9 stuff that doesn't exist on the old 3DS, so that would have to be defeated as well (I'm sure it's been broken privately, but you may as well just pretend it hasn't at this point).