Why does the new OS upgrade require a six digit passcode?

My mother is 90 years old. She has an iPad which she uses mostly to play solitare, though she does also use it for email and occasionally to find information on the web. She has never set up a passcode on the device. For the last week or two she has been continually badgered by Apple to update her OS. Last night she finally did, arranging for it to be done automatically while she slept. This morning her iPad, now with the newly installed updated OS, asked for her passcode, the one she never set up. Now she can't use her iPad. I contacted Apple and was told she could reset her iPad by using her iCloud backup, a backup that doesn't exist. Her only alternative is to erase her iPad, wipe it clean and start over. Way to go Apple!