IMO it comes down to maximizing your team-wide power.
Agreed. I mean, isn't that what pretty much every meta concept is about?
If your gank doesn't do anything, the question is then, "Does your teammate need to Recall?" Even though you're sort of weakening your teammate by leeching XP and gold, any Recall almost always loses you some anyway. So the quicker and more painless you can make your teammate's trip to base, the better off they are. And since you're getting some Gold/XP yourself, it's still a positive choice overall.
I'd say then it comes down to (from the jungler's perspective), "Do I stay in lane and last hit for a while, or do I shove the lane and get back to ganking/farming the jungle?" That choice is probably different at your elo, where the global pressure is a bigger factor, than mine. And based on a number of other factors.
But if none of those are true and your teammate just wants to sit in lane, I don't recommend taxing their lane for no reason.
In competitive LoL, and maybe your elo soloq, I'm with you 100%. In my experience at lower elo, though, if the gank was successful (gave me an advantage in whatever form), giving the jungler some more strength is often the best way to maximize team-wide power:
- If the jungler is pulling off successful ganks in my lane, chances are they're doing it elsewhere, too.
- I have a much easier time carrying if my team is doing well or going even than pulling us back from a big deficit, even if I'm relatively less fed in the former scenario.
- Once laning phase ends, junglers are often relatively less fed than their laning counterparts. If they have more gold, they have more ability to continue to make the plays.
- I'm usually able to win my lane even if I don't retain the advantage from every CS up I am, from the jungler gank that forced my opponent back (Karma is love, Karma is life).
So, in general, I'd rather spread power amongst my team, even if I'll scale better with that gold than my jungler will.