Since Cloudflare significantly reduces the load on origin + has WAF/DDoS protection, I would love if everybody had it. But unfortunately, customers typically do not figure it out themselves. Doing it for them involves sharing passwords, waiting for 2FA codes, and manually verifying all the records...
I don't think a big host could realistically hold all the domains on their Cloudflare account without an enterprise plan (their sales team would be calling you if they caught on), but I could see resellers benefiting from this. A reseller might be an agency with 10-20 clients all fully managed.
So if it were to be implemented, it should definitely not be limited to the MO.
Personally, to avoid a lot of DNS headaches, I am using Cloudflare for SaaS where users will only need to CNAME their domain to ours and Cloudflare handles the rest. The origin servers will not even serve traffic not coming from Cloudflare.