Well, some people do use manifold vacuum for thier advance, but the logic is lost on me and, like I said before, nobody has ever explained to me how having your automatic, hands-free advance (via vacuum) all in at idle makes any sense at all. I'd be happy to listen, just no one has ever offered.
Here's a story, since we're having a lull in the action...
Back when I was haulin' cars, my loads were about 90+% exotics, OEM prototypes, celeb cars, and classics. I pulled an enclosed trailer and there was a LARGE upcharge for that. Barrett-Jackson, celebrity car auctions, vintage poker run-type-ralleyes, SEMA show stuff, **** like that. (Seems like a dream gig, right? Reality bites) One of my most interesting pickups was a restored Model T Ford that you had to advance the spark by hand via a lever on the side of the steering column (there was also a hand throttle for setting the idle and, oh yeah, it was right hand drive. I had to pilot this alien onto my enclosed trailer, talk about a steep learning curve!). So I had this ancient man (spry, sure, but ancient nonetheless) teaching me how to drive his ancient car, keep it running, get a running start so I could make its 40 (or whatever) hp and 0 torque get it up into the trailer out in front of his Bel-Aire mini-mansion. I think me dumping the clutch with the revs at God-knows what while trying to keep the spark timing up, steer, aim for the trailer, don't crash, gotta stop when ya get on the lift platform, the brakes suck, the wheels are made of wood, oh ****, here we go, who's gonna have the heart attack first? Me or the old man? Could go either way...we both lived. And the car too.
The point is: vacuum advance was invented to handle spark advance, without having to do it manually, when you can't be there under the hood doing it by hand, ie: while driving. Connecting your vac adv to manifold vacuum applies maximum vacuum at idle, a time when you can easily advance/retard advance by hand by turning the distributor. Without a soliloquy on vacuum, suffice it to say, it makes no sense to me.
The End.