@gdgmacguy. That's one reason this can happen. Another reason is if you connected to a corporate Wi-Fi network. There are other scenarios, but they all involve getting corporate certificates onto your iPad. Here's how you fix it:
Go to Settings!General and look at or scroll down to the bottom. If you have an option called "Profiles" here, this is your problem. Choose Profiles and then choose "Remove" on each one. When they're all gone you'll be able to backup without a password, though you may need to enter it one more time (at least I did).
The downside of this is that you will no longer be able to access those corporate resources for which you originally obtained the "profile" certificates. Re-obtaining those certs will re-enable password protection of your backups.