The goal is to have max combustion pressure around 15 degrees ATDC on the power stroke, for performance use.
Advance is a crutch to help achieve that. Too late, and the piston is accelerating away from the pressure. Too early, the rod angle is bad and doesn't push on the crank
A lazy chamber, lacking effective squish area, has limited charge motion and needs a bigger head start.
High revs also need a bit more advance, as the flame front moves slower than the engine is.