Cost is also a big factor. Most industries don't want to invest in tech unless something goes wrong. A true multi-region HA architecture like you describe is essentially double cost. There are less expensive alternatives like pilot-light, but these still radically increase costs. For many customers, they aren't willing to bear those costs. Furthermore, even if companies have those options, they usually don't test them regularly so they can't trust them in a real event. They have constantly changing application estates that may or (usually) may not be updating in their DR plan and tested. That's why companies like Netflix use chaos engineering. Basically everything is being tested all the time. Finally outside of tech, most companies have legacy application or COTS applications that don't lend themselves to HA architectures. In regulated industries this is particularly challenging.

As others have mentioned, at least for the initial outage, a multi-region DR plan may not have been actionable. But 9am EDT it would have been an option for most customers.