You can play a jungler that needs to scale up, but still be present when stuff is happening.
As an ADC main, the most frustrating feeling I have is when I'm consistently out-trading my lane opponent, slowly pushing them in, getting ready to set up a kill in lane 2v2 only to get ganked and lose 2 deaths instead. I'd imagine the same feeling is everywhere else. It's not like they were baiting me, they didn't take bad trades over the course of the last 3-5 minutes with the plan for getting jungler aid. It's just that the enemy jungler saw that they needed help and my jungler didn't see the obvious countergank opportunity. Not that it's my jungler's fault - just that's the feeling in low elo. That you can't carry unless you get kills in lane, but you can't get kills in lane if the enemy jungler shows up whenever you're about to go for one.
If you see a lane that's setting up kills in lane without your help, it still makes sense to come sit by the lane while they do it. You lose what, a camp, to make sure they get a kill or two instead of your opponent getting a kill or two. Seems like a worthwhile tradeoff. You can even help secure the kill or take the tower afterwards. You don't need to be Lee Sin to win those battles - a slow scaling jungler is still more than enough to win a 3v3 or 2v2 when the enemy laners are almost dead already.
