Edison used lots of different companies for their own business cases and I think the Edison Illuminating Company only built electric generators. So indeed in the beginning of electricity, when the field was most untested/starting up, you did shop at special companies for a generator or lamps or whatever instead of using an integrated whole-in-one solution of a mega corp! Wikipedia:

> Edison Lamp Company, a lamp manufacturer in East Newark, New Jersey; Edison Machine Works, a manufacturer of dynamos and large electric motors in Schenectady, New York; Bergmann & Company, a manufacturer of electric lighting fixtures, sockets, and other electric lighting devices; and Edison Electric Light Company, the patent-holding company and financial arm for Edison's lighting experiments

These were only later consolidated into General Electric.