To me however it seems exactly right. Nobody execpt a Comic book villain goes "I will sell my soul to the devil for ULTIMATE POWER, muahahaha!" No, it's "I just need a little bit more Power to achieve my goals. I'll make a deal for a few magical tricks in exchange for some favors. If the Dark Power wants me to do some unsavory stuff I'll just hold my nose while doing it, how bad can it be?"
Yes, but I don't get the impression that any such process takes place, not when I read a build guide or advice in a thread. "Take a couple of levels of warlock. You'll gain up to 15 damage per round."
Now in fiction, the devil would be tempting the "dipping" warlock With increasing amounts of Power as he slides further into depravity, but in D&D 5E the Warlock class past Level 2-3 isn't particularly tempting for anyone seeking Power. The devil needs to improve his offer if he wants to fill his quota for fallen souls.
Ah, but there is no selling 10 or 15 percent of your soul. The devil buys the whole package at level 1. Or not really, perhaps. It depends entirely on whether the DM is stirred into engagement with that meaty hook, and whether he wants to take the whole table down that rabbit hole. In most cases, no, I think. And that is why we get the 2 level warlock dip. It's just bookkeeping. 15 damage per round.
I'm about to start a sorcerer at level 11 in an ongoing campaign. He may finish off with two or three levels of bard. Not warlock. I'm thinking tuba. Hasted tuba. Hasted sousaphone. My little fantasy character will have no master but me. The DM will have to be satisfied with just running the rest of the world. I will not offer him that leash, even if he is unlikely to tug on it.