The GPL exists because even under the policy you describe, there's no way for someone who gets a binary to also have the ability to get the source code.

As an example, suppose I'm Tivo. I make this cool DVR using the Linux kernel. It contains modifications to the kernel, a new filesystem, etc. Suppose also that you purchase the DVR, which comes only with a pre-built binary. Under the GPL, you also have a right to get the source code used to make the binary, and in a usable form. Which is why you can go to the Tivo site and download the source for your hardware.

Reverse engineering might get you the effective equivalent, after a lot of work. Redistribution right doesn't give you the right to source code.

The GPLv3 also uses copyright to require licensing of patent rights.

Do you not need these rights? Do you think others might find those rights useful?

I hadn't considered the relationship between GPL and patents. I'll have to read more. Off the top of my head, I don't understand how anyone who went to the time and expense of getting a patent could ever jeopardize it with a GPLv3 release, since there's no bright line between a version of your program and a completely separate program that merely links enough code in to get a free patent license.

GPLv3 and Apache 2.0 are the two most widely used licenses which specifically mention patents. The goal of GPLv3 is (quoting from the license) to "[assure] that patents cannot be used to render the program non-free."

See http://fsfe.org/campaigns/gplv3/patents-and-gplv3.en.html for a long discussion.

The "bright line" isn't always so bright. Consider if a hardware company pays MPEG LA for an MPEG license in order to sell a piece of video hardware based on Linux. The hardware company didn't get the patent, so while they must release the OS source under the GPL, they don't have the right to sublicense.