Two step verification

I just tried to log on and was stopped by the new Two Step Verification requirement. I followed the instructions and posted the emailed code. That gave me a new window with Backup Verification Codes, which I saved. There was a place to click to Disable Two Step Verification, so I clicked on that. When I tried to log onto sdc, I got the original Two Step Verification requirement. I went through the procedure 4 times, same result. This time I did not click on Disable Two Step Verification. and was able to log in.
Why are we being forced into a Two Step Verification?
Why won't it allow me to Disable Two Step Verification?