Because you live on that side: and as President LBJ said "Its always best to have them peeing out from inside the tent rather than have them outside peeing into the tent."
The silicone will eventually blacken and lift if it's constantly wet on the inside. Also as it only needs to be sealed on one side to stop any water from leaking out then it really only needs sealed on the outside to help finish and the silicone also gives the frame a bit more support.
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