Lets encrypt certs are only valid for 3 months. In many situations the auto-renewal stuff is inconvenient. Then its easier to just buy a commercial cert that's valid for a few years.
That's not so bad if you have to do it once a year or better yet once every two years, but I'm not doing that every 3 months.
There's an issue open to allow for the process to be automated, hopefully by the next time I need to renew it'll be available. But as it stands today I went with a paid certificate.
I was just looking at doing this last night for two sites and came to the conclusion that it was too painful.
Far too many products still require manual intervention which is a huge bummer. Synology, VMware, ddwrt etc.
OTOH, lego with Cloudflare DNS challenge proved to be very easy to use with a single command.
Of course that's still like a money printing machine, and wildcards and greenbars are much more. But the deal was pretty fine for my personal domain. To be frank, I would probably have renewed with them.