Except, Warlock pacts and contracts DO NOT cover all of the concepts of the sorcerer. They don't. A warlock is not covered under the concept of being left in the Shadowfell, exposed to the magical radiation of the plane, and your soul being altered by that magic. Warlocks. Make. Deals. That isn't a deal, that is radiation damage. A warlock cannot cover that concept. The closest you can get is that your parent made a deal, and you are written into that contract and bound by it, but that does not cover all sorcerer origins.
And the bolded part? That sounds like a mechanical problem that could be fixed, rather than an excuse to delete a concept that is closer to the actual depictions of magic than any of the other three classes in the game. We shouldn't delete sorcerer stories because they lack a good mechanical hook, we should FIX the mechanics.