On their dime? It costs nothing to keep signing iOS 6 for 1-2 weeks.
Unless you live near an Apple store, how are you supposed to be able to test before you commit to iOS 7? They only made it available in betas to developers, if you even know about it at all (most people don't).
One day, your device says it wants an update (which it's already downloaded perhaps), and like always, you press okay. Now, anything that goes wrong, it's too late. You can't go back.
Look around at how many bugs and design flaws you see people having. A 1-2 week reverting window wouldn't hurt Apple, but it sure would help its customers.
Look, I'm not arguing against the desire to NOT UPGRADE. It's just that it's up to you to perform due diligence. No one put a gun to your head and made you upgrade. Yes, Apple could have left 6.1.3 available but they didn't. Now it's time for the end user to take responsibility for their part.
I upgraded some of my devices, and didn't upgrade others. You know, it's kind of funny. The Walmart(s) here where I live all had iPhones (4S) running iOS7 for me to check it out and so did the Best Buy. I waited, I didn't jump of the ledge without looking to see how far down it was under me.
Those who leaped before looking are now upset about their injuries. I wish you could downgrade, but you ultimately pushed the button. Deal with it.