A thought on base movement speeds.

Why do champions who have low mobility also have low base ms (such as Anivia), while champions with mobility, such as Yasuo, Lee Sin, and Riven (yes I know all of these people are melee) also have high or fair base ms?

It doesn't make sense to me.

What do you guys think about this? Should it be kept as is, or should it instead be reversed, with Champions that have dashes/blinks etc have low MS to compensate, while immobile champions have higher MS to compensate for their lack of such tools?