Some ISPs inject their own ads on non-encrypted pages. It was a prevalent practice in Russia as early as 2007-2010. Not sure if it's true for other countries and modern times, but the technical point is still valid: by using HTTPS, this kind of attack on your personal blog is eliminated.
If your goal is to pass a certain message publicly, then the injection is an attack to your goal.
These injections often completely broke functionality of any even slightly non-standard blog engines, as they were not tested by the designers of the injectors.
