Not all servers have vote-kicking enabled. Mine doesn't, for instance, because it's very abusable.
Very. And abusable by the very people you'd want to kick! Often they come in groups of 2-3 and votekick legit players!
Anyway, what the game needs is a 'TK-Punish' system, much like Battlefield 2 and Battlefield 2142 had. If someone kills you, it gives you two options:
Page Up - Forgives the TK. Used when its obviously an accident. Nothing happens to the TKer when you forgive
Page Down - Punishes the TKer. Punishing does various things, based on the server settings.
Since you respawn in BF 2 and BF 2142, punishment makes respawn times 30 seconds more than usual or longer! And it gets worse with each TK, usually having the TKer kicked after 3 TK Punishes in a row.
In Killing Floor, you could make the TKer sit out a round (Or two rounds for a repeat offense!), lose all money, or get outright kicked. You could set it up as well that after a number of kicks from a TK-punish (Meaning you killed people 3 times in a row multiple times!), you are banned from the server, only able to be unbanned by contacting an admin and making your case.
The system works great in Battlefield. Griefers are quickly kicked or at the very least, slowed down and yet it doesn't punish accidents. Since Friendly Fire isn't the default setting, I can see why they didn't include this feature in Killing Floor, but it'd be a nice thing to add and I'm sure that with some scripting, server admins could code it in...