Magic is a highly strict and rigorous craft.
Especially when it comes to magic related to human transformation, the related norms and requirements are extremely stringent. For instance, wizards who are first introduced to transformation magic need to sign a confidentiality agreement and a host of authorization documents, back up and retain relevant skin cells and blood samples, and leave their names in the relevant records of the Wizard's Alliance.
In addition to specific cases of wizards, any wizard practicing transformation magic needs to report their post-transformation shape - partly to supervise these wizards in charge of transformation magic if they seriously fulfill their promises, and partly to protect them.