Why haven't Eminem and Justin Timberlake collaborated yet?

I know Eminem dissed Justin's ex back in early 2000s when I was a kid
in some song, but other than that, WTF is preventing in the making of
a sick duo?

Justin is great singer and awesome in rap collaborations like TI - My
Love, Dead and Gone, 50 Cent - Ayo Technology, and bunch of Timbaland
beats.

Eminem ft Justin Timberlake produced by Timbaland and Dr. Dre. Add in
a small part from 1 of Rihanna/Katy Perry/Bieber/Gaga in there maybe
and I guarantee this track would be the #1 Youtube video of all time.