List of free temorary email solutions.

https://www.guerrillamail.com/

https://10minutemail.com/

https://addy.io/ - this one is slightly different

and about a billion similar ones.

People don’t know about GIMP and are allergic to trying new things.

Also speaking as someone who started with GIMP and then had to use PS for a class the change of UI is really painful if you are used to something, given how complicated photo editors are.