Comment by charlesbarbier

I didn't express myself well but what I meant by force is that by building a standardized to automate way manage certificate, ACME imposed itself and became mandatory.

Previously, most CA had no programmatic way to order certificate, it was all done manually.

As far as I know, the only providers with that would let you automate certificate provisioning at the time where Comodo, GlobalSign and Digicert.

They all had their own quirky API. Just to give you an idea, we ended up selecting GlobalSign at Shopify a few years before LetsEncrypt, and it was this SOAP nightmare: https://www.globalsign.com/en/repository/GlobalSign_Client_A...

At first none of them were warm at the idea of providing an ACME endpoint. I'm assuming part of it is the cost of implementing it but they probably liked the stickiness of their custom APIs too tied to million dollars contracts.

Nowadays they all implement ACME. At some point, they where effectively forced to implement it to acquire new customers and keep their existing base around because nobody would accept poorly designed custom made protocol anymore.