It's definitely a thing.
It makes a difference to me flying a Cobra III.
I'm friendly with Feds and Imps. Taking a single delivery mission for a minor faction aligned with either of those will take me from Neutral to Cordial. It'll take 2 or 3 delivery missions to do the same for an independent faction.
Alternatively, if you're selling Exploration data, it'll bring it down from ~6 MCR to ~4.5 MCR.
It's one of them things where you either do it "the fun way" or "the quick way".
"The fun way" is always just to be natural, but putting any kind of difficulty gauge on this is difficult because you always know you're bypassing the "easy" ways of doing it.
Unfortunately because "the quick way" exists, and I can just use any semi-decent trader to trade rep in over a few minutes, any situation where you're adding length/difficulty for the sake of it...well, can you really put a metric on how difficult that then should be?
Simple way of putting it: faction rep/rank needs an overhaul. When the time is right. And should be more involving instead of allowing me to trade myself to Allied in minutes. Which I don't need the cutter to do -_-