If you get a longer sock, it isn't like extending the straw into the tank. It literally does nothing to help you suck up more fuel. The "straw" if you will, is where the sock attaches to the pump. That's where it achieves a vacuum to suck up the fuel.
Think about it, the sock is full of holes. Extending a hole-filled-sock lower into the tank won't allow it to suck more up. If you have two drinking straws for your shandy on a Friday night, one is a normal length and the other is a metre long, and both of them have holes all the way down starting 2 cms away from your lips, is the meter long one going to give you more reach? Nope.