When I shot weddings for a studio, we agreed by contract to carry back up equipment.
When the owner asked me what my back up camera was, I replied, tongue in cheek, "An Instamatic with a pack of flash cubes"
He laughed, but added, "An Instamatic with flash cubes would do a good job in the right hands"
We settled on my using a Pentax to back up my Rollei, and I eventually bought a Mamiya TLR along with a second Braun RL 515 flash, with a spare Honeywell sync cord in my jacket pocket.
I can see "professional" used in terms of lighting equipment. You need something with punch to shoot at any distance with high ceilings, after all, the light takes the picture, and not everyone wants available light for everything.
People still seem surprised that a P&S flash does not often work well for 20 foot shots.
Regards, John