Because it's more work? Also 2fa often fails for the rightful card owner. And Cloudflare overzealous "security" is one of the reasons for failure.
There are several colliding problems there (cheap cell phone plan, 2fa being via text, online purchases requiring 2fa) but it still illustrates to me the pain of doing simple stuff in the modern tech space. I wish the powers that be would work harder on solutions that don't require extra work from the people doing small, normal stuff. It would be better to have a lot more fraud occur but a lot more of the perpetrators pursued and caught. A lot of anti-fraud measures seem to be largely about passing the buck to someone else instead of actually eliminating the humans who are driving the fraud.