XMSS MT for height 80 The XMSS RFC supports only tree heights of 60, which makes the chosen keypair to sign up to 2^60 messages, which is not practical for the use of SSL and so on. The paper https://eprint.iacr.org/2017/966.pdf mentions that it is possible to increase the 60 number to 80, which would be sufficient for SSL use. Why is this treeheight not supported in the RFC?
Why is this treeheight not supported in the RFC?

I'm not Andreas, and he did not mention this to me specifically.  He has mentioned that the CFRG did ask him to limit the number of parameter sets he defined.  My speculation is that he couldn't imagine any situation that would need more than $2^{60}$ signatures generated from a single private key.
Do you have such a situation?  Even if you were able to generate a signature in a nanosecond (which is far faster than what is achievable today), it would take over 36 years to use up all $2^{60}$ signatures - do you have a use case that would go beyond that?

he XMSS RFC supports only tree heights of 60, which makes the chosen keypair to sign up to 2^60 messages, which is not practical for the use of SSL and so on

Why would $2^{60}$ signatures not be sufficient for TLS?