But they also require close proximity and a fair degree of training/practice for accuracy (beyond 25ft), and most common handgun calibers will not penetrate bullet-proof vests (with a frontal hit), requiring a head shot for lethality.
Tell that to these guys:
http://www.freerepublic.com/focus/f-news/2979959/posts
Assassination Attempt on Bulgarian Opposition Leader Ahmed Dogan (MRF)