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Because their faces are all wrong?
They have these strange pincers instead of mouths (or something even weirder), either giant segmented eyes or dead-looking dots, weird creepy scales and hair, various mandibles, antennae and other weird shit.
And they're hexapodal instead of quadru- or biped to boot.
Also, we're not used to see them this large, so when you look at a zoomed in photo, you're surprised.