Why can't I choose the option to turn off Two-Factor Authentication?

Please refer to Two-factor authentication for Apple ID.

Excerpt:

Can I turn off two-factor authentication after I’ve turned it on?

If you already use two-factor authentication, you can no longer turn it off. ..

LisaD2468 wrote:

Why can't I choose the option to turn off Two-Factor Authentication?

it's required to use some of the latest features of iOS, macOS, and iCloud.

See: Turn off two-step verification

ref: Switch from two-step verification to two-factor authentication ...

Two-factor authentication for Apple ID - Apple Support