It was because the U.S. government placed export restrictions on Rijndael. I mean, the alternative might have been for them to just use Rijndael anyway, and tha

It was because the U.S. government placed export restrictions on Rijndael. I mean, the alternative might have been for them to just use Rijndael anyway, and that would probably have been better in the long run, but heh. Now that that stuff is out of the way, I honestly can't see why they don't (or didn't until recently?) allow Rijndael or ChaCha20.