Minecraft Skins aren't working on Multiplayer Servers

Put the summary of the bug you're having here

The Minecraft Skins on servers are able to be seen.

Minecraft Skins not working at all on any multiplayer server.

1. Log on to any Minecraft Server. Make sure it is full of people and you are playing Minecraft 1.7.9 or up.
2. Observe how many Steve Skins everyone has.
3. Now observe how many custom skins there are.