They literally have hundreds of voices in skyrim for NPCs. I'm sure giving 10 more customizable options wouldn't hurt.
Bethesda says that there are at least 20 shouts in the game, yes?At least.There are ten different races and both genders for each race.20 times 20 equals 400, if you multiply that by ten that would equal 4000 files, and I didn't even count the damage grunts and power attack grunts.That's valuable disk space that's probably already being used up for NPC voice actors.I think people would rather have diversity in the NPC voice actors than the ability to slightly change the pitch of your character's voice when there isn't even that much voice acting for the character.If you watch the third video and move it to 4:30 you can see his magicka go down by a lot when he does the "Dovahkin!" yell, so he's probably just charging up a high-level spell, and the yell was added over that, and I don't think you shout "Dovahkin!" every time you cast a high-level spell.