The number of lights required for a shot is dependent on the look and type of shot. There are brilliant portrait photographers that use one light and that's it and no one is telling them they're wrong or not professional.
Some shots require complex lighting with 4, 5 or 6 lights. If you need it you need it but there are also photographers that just pour light all over a shot haphazardly and have no clue what they're doing.
Product photography will require different setups than a sitting portrait. Group shots require different setups. A set that is 15 feet wide and needs to be lit for pure white, has a main light, a fill source, and 2 edge lights requires 6 lights.
Great lighting is not about the number of lights. It's about the subject, the intent, the product, mood, and a host of other variables.