Anyone that wants to bring something new to our projects needs to prove what is the business value. If it reasonable, it gets adopted.
So for Scala to be adopted on our projects, customers need to be convinced what is the business value of having their multi-site team learning it, instead of us using their already installed infrastructure.
I can dabble in alternative programming languages on my hobby projects.
This already rules it out from our projects, due to the way our customers manage their IT stacks and development environments.
So I don't need to ask permission to several IT departments to have C# on our projects, but I do need to do it for Scala.