Equo is installing pre-compiled packages so the USE flags are already set during the original compilation. If you wish to compile programmes to your own specifications then you need to use emerge. It is not a good idea to mix the two but, generally, to stick to one or the other.
Self-righteousness is a loud din raised to drown the voice of guilt within us - Eric Hoffer
Don't believe what it says on the right - I am anything but sagely; More oniony!