Because they're incompetent. Literally just a week ago a report (https://www.bleepingcomputer.com/news/security/godaddy-hacke...) just describe how GoDaddy is simply incompetent with security. This is in addition on having one of the worst customer support of all major registrars.
A customer of mine had their website hijacked by Godaddy (copied their website text and pointed to a Godaddy IP). The application stopped working of course because that was hosted elsewhere (with me). They did this because they didn't like what was being sold on the website.
Because they are shady. I wouldn't put it past them to somehow claim they didn't receive renewal payment for the domain then take over ownership of the domain and then charge/sell it for an absurd amount of money.