Because I totally want to see Victor von Doom make a guest appearance on 'Agents of SHIELD'. It would be so awesome to see the fight between him and Daisy Johnson.
Think about it--she'd blast him with seismic energy, shouting, "You're nothing but a relic--an outdated footnote to history made of obsolete technology and outmoded ideas. Oh, you've made your attempts to update yourself, but nobody cares anymore. The world's moved on without you."
And Doom blasts back with energy bolts, declaiming, "Relic? I am an icon! I am a legend, the cornerstone of the world you made. You think you would be anything without me? You think you're anything now? You're nothing but flash without substance, a few marginal improvements on a design I conceived. I am no footnote to history. I AM history."
And in the surprise finish, the Vision shows up, phases through both their chests to knock them unconscious, and says, "You're both obsolete. Unreal FTW!"
(Yes, this is a terrible joke.)