Its a bit harder to control how much collateral damage occurs with A2G missiles. Put a rifle on a humanoid robot or small explosive on a drone like in Slaughterbots and that’s much more terrifying.
(To this day I remember this one thing about US drone strikes in Pakistan I read in an article many years ago: the people living there became literally afraid of the blue sky - as the drone strikes tended to happen during good weather. That's terror.)
Biped cyborg killer is just not a realistic weapon. The slaughterbot attack on Maduro in 2018 shows that technology is not very mature yet.