Same here, I just set up LetsEncrypt for a second site last week and didn't know this. From a glance at the docs it looks like it's relatively new. Ubuntu 16.10 has the automatic cron setup but not Ubuntu 16.04 which is what I used.
That's strange. I swore last year I would never use a non-LTS version for a server. Unless I'm missing something, it seems to be more headaches than it is worth to roll with the XX.10 vs XX.04.