What was the purpose of giving Nasus passive lifesteal?

Legitimately curious to this. Personally I have no beef with Nasus when I lane vs him. I find it easy since i'm not some retard who pushes the lane and lets him cs under tower.

Back to the question though, Nasus is suppose to be a late game god (since he technically is a god according to lore) so why does he get such a safe early game with in built sustain? Around level 1-5 it's fine but at level 6 it becomes annoying to try and keep him down only to have him lifesteal it all back up within a couple of hits. (especially since Lifesteal procs with his Q for whatever dumb reason)

I thought the entire point of a late game hyper carry being balanced was the awful early game trade off. Take yasuo for example, he's insanely easy to shut down early game but if the game goes on too long he's gonna start trashing your team. Same for vayne/jax (not tristana she's just bs with that stupid self-peel)

I honestly don't get why a person who is suppose to have terrible early game gets in built sustain