Poison darts were preferable over more direct assassination means for several reasons. First, with an appropriate toxin, the victim's death could be nearly-instantaneous, and essentially guaranteed. Secondly, the use of lethal toxins often incapacitated the target before he even realized what was happening, protecting the identity of the attacker and allowing time for escape. Because of these reasons, these exotic weapons were used by various bounty hunters and criminals across the galaxy, most notably Jango Fett and Jodo Kast. The only drawback is that they had a relatively short range.