Why would Super Smash Bros 4 come out for NX when NX will back backwards compatibility?

[Darwinianevolution]

Also, even if it doesn't get WiiU BC, it could always have 3DS backwards compatibility. After all, with all the rumours of the NX using cartridges, it may be better to keep those games around instead of the WiiU ones, that can always get a quick and cheap remaster.