How has no one made a coin that can be mined at the same time as other x11/x13?

[Acidyo]

Are they hard to make?

I remember the coin that came out that could be mined at the same time as Vertcoin but no one has seemed to do anything about x11 or x13. Wouldn't it be a good feature to be able to mine more of these coins since the algos are currently asic-resistant?

[Instamatic]

Well, technically you can mine an X11 coin with your CPU and a scrypt coin with your GPU.  I've done that before to little effect, better a month or so ago when the network hash rate for Dark wasn't so high that my CPU plugging along for 300 kH would at least net something at least noticeable.