Really? Both are pretty instinctive to me, I do them with little thought. I even switch capslock on and off mid-password without thinking about it to type a capitalised portion.

Yes really. Anyone can hit ok, but not anyone knows the admin password. Someone can't walk up to your machine while you're away and install software in Linux, they can in windows. Hitting Ok is not sufficient. The point of sudo is to verify your identity, an ok prompt does not do that.