If you are the best player on your team and you bot you will get the most points. If you are on a team with people on your level and you play bot you will probably not score much. Bot scores fewer points than top on average. Just because you can carry your team from bot doesn't mean in equal situations bot doesn't score fewer points.
If your team holds windmill, what is the rest of the enemy team doing? Probably making your life hell at bot. If the enemy team holds windmill, you're free to push and farm.
I've kind of learned the hard way over my last few games, that if my team is actually doing well at top, I can't push safely and I'm probably going to be getting ganked repeatedly.