Also, the argument against giving Sorcerers extra spells is that they eventually end up with more prepared spells than a Wizard of the same level, which definitely steps on the Wizard's toes.
That's kinda the point. The Wizard changes his prepared spells every single day. The Sorcerer's spells known are the only spells he'll ever be able to cast-- so he really should have more of them. The current status quo is an incomprehensible oversight.
Doubly so, given the Sorcerer also has a narrower list of spells to choose from.