Why editing the two default GPOs is not advisable?

Editing the two default Group Policy Objects (GPOs) is not advisable because it can lead to unintended consequences that affect the entire domain or organizational unit. Default GPOs are designed to provide baseline settings and security configurations that ensure consistency across the network. Modifying these can complicate troubleshooting and maintenance, as well as hinder the ability to apply updates or revert to a known good state. Instead, it's recommended to create new GPOs that inherit from the defaults, allowing for customized settings while preserving the integrity of the defaults.