This the typical mindset around here. Deny, deny, deny.
The problem with adding a brim to the entire model is that you have to remove an entire brim from a model in post processing. Why would I want to add time and material for a brim on regions that don't really contribute to lifting in the first place? Just put it exactly where it needs to be.
Adhesion discs should be a slicer option since it's so specific to FFF in the first place. Until that happens, we have to rely on grey matter where available.
If you don't believe me, then try it yourself. Print a long, tall, thin object with significant double overhang. Something that pushes your printer's dimensions. Print one with brim, and one with two adhesion discs. In something like ABS. See which one takes longer to print, wastes more material, and takes longer to post process.
Again, the designer knows up front: "this is a long thin object with double overhangs that will be prone to lifting" and "I am designing this specifically for FFF".
Why would you not adjust the model to increase its likelihood of success on a wider range of printers?
Because what exactly?