Why would you still want to opt for a Drupal multisite setup? What strong reasons are there for using this Drupal 8 feature?

I mean when there are so many other tempting options, as well:
 

• you could use Git, for instance, and still have full control of all your different websites, via a single codebase
• you could go with a Composer workflow for managing your different websites
   

One one hand, everyone's talking about the savings you'd make — of both time and money — for keeping your “cluster” of websites properly updated. And yet, this convenience comes bundled with certain security risks that are far from negligible.

Just think single point of failure...