If you want to send games to people over the internet, people might not have burner emails(or just not want to share their email address) for that kind of stuff. I just think this would be a good option to have in addition to email gifting.
You can gift games by checking a box on checkout, and then you can send the download key to an email after paying for it. If they have an itch.io account the game is then linked to their account upon claiming it.
I just ran into this with my sister, who's used the same username everywhere since we were kids so it's easy to find her profile but less easy to know what email she's using lately. Would be nice not to need to ask!