User blog comment:Otakon7/Otakon7's Buddyfight Simulator/@comment-27015084-20150926171749/@comment-2234004-20150926191601

Several reasons, but the main ones are identification and contact.

The original purpose was to provide and reset passwords (which is what emails are used for in registration) but due to some restrictions of my server, I had to skip that step and imprint passwords directly.

Emails and passwords are encrypted so I am the only one who knows how to decrypt them btw.

You can freely enter some random email however, at this point the only factor is that it must not be an email in use by the sim. It would just mean I'd have no means of conacting you myself should any issue arive (hasn't been any so far though).