Don't make up email addresses

Why do people do this?

I have a junk domain, one I use for signing up for stuff, and which works. It usually has the name of the place I used the email address in the address. E.g. youtube@example.com for signing in to YouTube, though obviously example.com is just an example and not my domain.

Some idiot keeps signing up for instagram and using my domain.

This is annoying. But also it is pointless, as I am now simply using the "forgotten password" on instagram to set a strong password, change the profile pic to something rude, set default date of birth, change the name to "Idiot using my domain", confirm the email address, and turn off all email notifications.

It is rather odd of instagram, by the way, that they see my login as "suspicious" (presumably as from a different country even) so they send a 6 digit security code for me to enter. What is odd is they send that by email, to the same email address they just sent the password link. What is the point in that?

So the idiot does not get to use the instagram account at all.

What is weird is that not only do they try and login to it (which just makes instagram send me a "you are having trouble" password reset link), but they have even tried the "forgotten password" link that emails *ME* a reset password link. Why do that?

At one point they tried to change the email address on an account - not sure how they did that - maybe it is one I had not set a new password on yet - but I was emailed and given the option to revert that change and confirm my email address. So I did. They were trying a Russian email address.

If his keeps happening, I'll make a small shell script to automatically zap the login the second they create it!

By why do it? Why use someone else's email address on such things? What is the point?