Well ... actually, a lot of interesting results can be achieved, with JUST a spot-light, alone and no other lights. A lot of people get carried away ... it's easy to be seduced with equipment.
As one lighting expert once said, the moment you introuduce a flash, technical control becomes more difficult by 3x. Imagine introducing 2, or 3 or 4 flash.
I personally always take one extra light than I think is needed for a particular job...just in case, but I always try to build up from natural light, then bring flash in only when all possibilities are exhausted. Mind you, I have been in situations where more than 5 or 6 (or was it 8) lights were needed ... and it takes an entire day just to set-up and test, just to get the correct balance ... and we're talking about seasoned professional comnmercial photographers doing this.