[Gaz64]

There are many reasons.

One coil with a distributor has many places for failure: only one coil, which works harder; long ignition leads, rotor to cap gap (spark has to jump this gap as well as the spark plug).

Multi coils: engine will still run with one coil failure, more "off time" for coils which extends their life, short or no leads, no other gaps to jump, no distributor to fail (rotor button, cap, pickup assembly).