Manifold Vacuum Advance what am I not getting?

Well that is your 'typical' engine that we see folks asking about the use of MVA:
- 12:1 CR.
- 255 @ 050 cam
- tunnel ram with 800 cfm carbs.
- revs to 7000ish

Yeah everybody has one, there are three in my street alone.....

That engine would STILL idle better with more than 20* initial......whether you are honest enough to admit it or not. One way to add idle timing is MVA. It is not the only way. But MVA is simple, inexpensive & reliable. And sure, you could run with 5* initial timing. But it would not be the most efficient, & the engine would run hotter. Why wouldn't you [ or anybody else ] want the engine to run as efficiently as it can???? One reason you are running 12:1 & 0.040" quench & not 10:1 & 0.125" quench is because you want maximum efficiency.