Offlaner rotations to help your carry?

Curious what the strategy is behind leaving lane and letting opp carry farm safety versus helping your struggling carry. As an offlaner I notice position fours don't rotate as much as they used to and basically just baby sit me. Carry is the win condition so helping him seems like the highest priority.

If the position four isn't going to rotate should I tp to help my carry or stay in lane to prevent opp carry from free farming?