I was wondering if journals that publish regularly formal proofs are indexed in journal databases like Scopus or Web of Science. Apparently, this is not the case. Why is it so?
In computer science, journal publications are often less valuable and important than publications in conference post-proceedings. They are typically not indexed in databases that focus on journals, even if they constitute the prime mean of dissemination and peer-reviewing.
A number of conferences exist which focus partly or totally on mechanized proofs, such at Certified Programs and Proofs or Interactive Theorem Proving. Within the community they are considered in a very similar way to other conferences not focusing on mechanized proofs specifically.
So the absence of indexing in this case is a more general issue with practices in computer science, which are not specific to mechanized proofs.