Front end developers know how to use this technology. They know this technology very well, so will be way productive.
No weird new template language to learn and install on every single project.
No dependency on a rapidly changing server side backend... or database, or 3rd party API required.
Being able to use the templating system either via the browser, or via the server side means there is no dependency between the front end and the back end. Front end developers just need an example json file to work from. Then the back end developer just needs to create the json file.
You are (currently) using the wrong templating system.