You don't get it. If the hacker was able to change the email address instantly like what happened to us here then we "instantly" don't have and can't access our accounts anymore.

If he can't change our email address instantly, then the account won't do him any good.

In some cases like what you're stating before, what if both account and email was hacked? Then that's where the 24 hour process comes in.

Let's say you can't access your account so you use your email to retrieve it, (you can still retrieve your account using your old email because it takes 24 hours to update your profile)  but what if the email was hacked as well, then you have 24 hours to retrieve your email before everything goes into shit.

It's very easy to retrieve email accounts as long as it's really yours.