transloadit appears to fall back to other languages for systems they probably aren't confident enough to use Node.js for (ex. payment processing)
Our website is written in CakePHP. That decision made sense ~2 years ago when there was no express, npm, etc. combined with the fact that we were former CakePHP core contributors.
If we were to do it again now, we'd do the website in node.js as well, as that would allow us to share domain logic. In fact, if we find the time, we might migrate even now.