Like many people FFT was my introduction to Canvas. I met the instructure team at, ahem, a certain LMS themed conference that was held in Las Vegas, went up to my room to create a FFT class and have been hooked ever since. At first I liked it for learning myself and showing to colleagues. Then I like it because it was a way for me to access Canvas that wasn't tied to any formal RFP processes or subject to any external rules. As we moved along and were using Canvas in a consortium when many institutions that had their own instances, authentication methods and policies, FFT because for me a kind of neutral country where I could continue to experiment, conduct training and do group projects, working with people from multiple institutions, without getting bogged down in turf or bureaucracy issues. Now, even though I have access to my own test instance, I still like FFT because I can have multiple student and teacher test identities totally separate from my official work site.
At the core I think the reason I like FFT is that it is, well, free and it is egalitarian - anyone can use it and I like to think I am using the same tool that is being used by people around the world, crossing many boundaries and socio-economic levels. Even if I could to the very same things in a different instance of Canvas, I guess I just think FFT is cool and like using it.