What is the purpose of the early game 25% assist gold nerf?

I see no logic in punishing supports in assisting early game kills. i find it very depressing to score my buddy first blood only to receive 100 gold while he gets 400.

supports stealing kills is bad enough already, now there is even more incentive to do so, especially early game.

i demand an explanation at least, the snarky "don't let lee sin take the early kill" text offers zero explanation for this decision and genuinely pisses me off.