[pseudalopex]

ZeroSSL offered for free 3 single name certificates. The next plan was $180 yearly.

Actalis offered unlimited single name certificates. Why are ZeroSSL more popular?

Google offered unlimited certificates with multiple names and wild cards. But they required a GCP account seemingly. It would require to give Google personal information, a phone number, and automatic payment permission. And Google not disable your account because your spouse uploaded images for your child's doctor.

All others I saw charged for each certificate.

[dizhn]

It's popular because Caddy uses it. I am not sure if it's default or just an option though.