Term reference is not available as a contextual filter for a View. Why not? I have a commerce product of type Album. On this content type is a taxonomy term reference. This term is from the vocabulary 'Our Artist'. In other words, every album gets tagged w/ the artist name that comes from the 'Our Artists' vocabulary.

I'm trying to create a view that groups together all of an artist albums. I want to use this taxonomy term as a contextual filter. But it is not showing up as an option in the contextual filters list. Can someone explain why?
As mentioned in Niall's comment, you will want to add the taxonomy relationship. In a view that I created recently, I used the Content: Taxonomy terms on node relationship. Once I added it, Content: Has taxonomy term became an available option under Filter criteria. 

That is only one way of doing it. There are a few different taxonomy relationships which serve unique purposes. I'd experiment with them to see what fits your needs.