When helping a teammates lane doesn't help (Low Elo)

Sometimes in game you find you've pushed your lane and are easily winning but see a teammate that appears to be struggling. This isn't always the case. Just because a lane is pushed and under turret doesn't mean they need (or want) assistance. This is especially in the case of Nasus or Veigar. You coming to that lane does two things:

1. Brings enemy attention to that lane causing them to collapse on it and/or camp it.

2. Because they've had you come they know to watch for that and are less likely to be killed by an actually gank.

If your teammate pings you to not come to their lane, don't. You're probably helping more by not.

Again in the instance of Nasus / Veigar (but could be applied to almost any champ) if you come to lane and think "I wasted some of my time, I'm going to tax" all you do is push the lane to a point where they cant safely farm/stack and you effectively make the game a 4v5 since you've taken away your teammates ability to become effective in the game.