Why advance timing?

Mine was not moving after my up dates, must be a low vacuum draw on the 390 4 barrel , because it works pulling a vacuum manually myself, I just don't think I had enough vacuum for it to operate correctly, I believe I am running a ford Carb now, and the vacuum system are not matched anymore . A recurved Distributor does not use vacuum, it reads and advances on it's own, If I had the fists picture set up I had (first picture) the vacuum may have worked but I never checked