Erase All Content and Settings not support

Erase your Mac and reset it to factory settings

Below is an Excerpt from above link.

Notation is that this features is only available to Mac with Apple silicon or the Apple T2 Security Chip

Use Erase All Content and Settings to quickly and securely erase all of your settings, data, and apps, while maintaining the operating system currently installed.

Use Erase All Content and Settings

This feature requires macOS Monterey or later and a Mac with Apple silicon or the Apple T2 Security Chip. Learn what to do if you can't use Erase All Content and Settings.

As mentioned…

It has to be a Mac with Apple silicon or a Mac with the Apple T2 Security Chip.

This feature is only supported in fairly recent macs - maybe from about 2018 on. What is your mac model and year?