Put yourself in my shoes. You'd been a member for years, almost 3000 posts, hundreds of thousands of points of hard-earned reputation. Your account has got you work. It's something you value.
Then some scrot hacks your account. Clicks delete. Everything gone. How would you feel?
So instead, there's a process. You talk to a real person. They work out if you're really who you say you are, and instigate a deferred deletion. That gives your account 24 hours with a banner over the top, allowing you to cancel the deletion request.
This provides some protection from hackers, some protection against impulse. I can understand your misgivings —given your expressed intentions— but it's a feature and one I'm very happy exists.
The trade-off is it takes a little time to execute. A human has to be poked in the eye a sufficient number of times —or finish what they were doing— to get to your ticket. Ultimately, I don't see that as a problem because if you want to stop using the site, you only need close the tab and walk away. Having an account (in the process of deletion or not) isn't time sensitive.
I've seen morality pop up a few times since the question was originally asked. When you joined the site, you essentially agreed (per various terms of service, not a quote) to:
Do stuff to make the site and the internet a better place.
What's what SE is all about.
But a lot of people who want to leave attempt to take a vast number of their posts with them. These may be the accepted answer, or just another good answer, or comments that explained the context. Removing them removes a net good from the internet, running contrary to what you agreed to.
So again, the system balances what you want to do, and what is best for it. There might be very legitimate reasons to delete more than 10 comments, or answers, or whatever but chances are somebody is trying to wipe their account clean. Again, contrary to the rules.
Again, I this as a feature of the system but I can see how it might be surprising or frustrating. We could probably debate the morality of this at a very deep level for a very long time but it won't change the outcome.
My interest —to be very blunt— is protecting the site, not making you happy.