I’m afraid how much sensitive information transits through email services. Notably, all credentials to access accounts, and possible viruses. Maybe, after the buyer takes ownership, they realize the immense liability it is, and decide to get rid of it.
The same is true for services that offer "Login with Google" etc.
It's actually really bad that I can sign up with many services using a traditional email and password combo and the "Login with..." options work straight away. They really should be opt-in for security.
Feel like I've had "oh here we go, incredible journey that needs me to reconfigure everything" a few times now
e: in fairness to Mailgun the most recent one I was thinking of (Pathwire) was a branding thing not a purchase