Question

Drupal provides a WYSIWYG editor by default.

Answer 1

Drupal does not provide a WYSIWYG editor by default but it can be downloaded and the extension can be installed in the device that the end consumer is using and hence it is possible to get it on the platform but just not by default.

Drupal believes that it is not required to be provided by default and that when required the consumer will download it by themselves.