Yep without assistants they do have pluses.
Surely some of the big lights isn't that expensive. You could go manual speedlights but when the SB800 was in NZ they costed up to $900, I got mine overseas ..
The thing is if you are photographing people they don't have a lot of patience for you to do test shots LOL.
I Just Have Cameras and Stuff
I don't have an Artistic Eye - I have a Technical Bent & a love of GadgetsGive an Artist a box of different sized colour blocks and he will create an art work; give me the same box and I will sort it by colour and then size :)
But in general from all the people who have them, I think most people don't use them outside. For indoor use like at home or in a studio, big lights have a lot of advantages. Some of the children/wedding people I know who work as full or part time that once was just a hobby. They tended to go v light given the fast PJ style they might just have 2 speedlights with a little wee softener attachment with bungy cords or bookshelf clippers or something or just bounce where they can and leave all the stands back home.
If you want to start cheap, check out Yongnuo YN-560II flashes on ebay. Pretty much the same power as SB900/580EX for $100 NZD. No TTL so all manual, but good for slaves. I've just got one and so far its all good. Add these, a stand and an umbrella, and you've got a simple off camera setup for about $200-250 NZD.