There were a bunch of drivers to move to git: 1. DVCS has some great workflows. Local branching, transitive merging, offline commit, etc. 2. Git is becoming the industry standard and using that for our VC is both a recruiting and productivity advantage for us. 3. Git (and it's workflow) helps foster a better sense of sharing which is something we want to promote within the company. There are more but those are the major ones.
I'd have to dig up the link: a few years ago our VP had a good blog post on why we chose to add a Git server to our offering. TFVC is a classic centralized version control system. When we wanted to add a distributed version control, we looked at rolling our own but ultimately concluded that it was better to adopt the de facto standard.