The whole point of the primary (low voltage) circuit in a coil is to flow enough current to build up a magnetic field around the secondary (high voltage) winding. When the primary current flow is interrupted by either opening the points or turning off a power transistor or two, the field collapses and induces voltage into the secondary winding. The stronger the magnetic field is, the higher the secondary voltage will be. Coil magnetic induction is measured by a term called "ampere-turns". The magnetic field gets stronger (hotter spark) by either increasing the number of turns of wire in the primary winding, and/or increasing the current flow (amperes).

Conventional points have an upper current limit of about 5 amps. Solid state trigger units like the GM HEI or the Pertronix can carry much higher current because there's no mechanical switch (points) to arc and burn. Combining a low resistance/high current coil with mechanical points is inviting disaster. The ballast resistor protects the points by limiting the primary current during normal driving to a level the points can handle, while still allowing for a hotter spark during cranking by bypassing the resistor when the battery voltage drops due to the load of the starter. Using a coil with a built-in resistor results in a weak spark when you need a hot one- - - -during starter operation in very cold or very hot conditions. The Delco research engineers figured all this out way back in the mid-1950's when they designed the 12 volt ignition system.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!