The problem is that despite being deployed and having a lot of support there still is no official RFC for X25519 in TLS. We have only an RFC for the curve as a

The problem is that despite being deployed and having a lot of support there still is no official RFC for X25519 in TLS. We have only an RFC for the curve as a cryptographic primitive (RFC 7748). A bit unfortunate that IETF process runs so slow in this regard.