It was meant to be that way, so a powerful wizard would have everything he needed right at his finger tips.
Yes, but there weren't always alternatives. With every magic skill, you would be able to do everything, but you'd need far more than 6 skills to achieve the same with no magic.
Magic completely removes the need for Speechcraft, security, sneak, all fighting skills, armour (shield) etc. And each magic skill could do a variety of things. You don't see security letting you do more than opening locks.