I am sorry, but I love the 'robbing life modifier' expression used by a few here. How about calling it a light diffuser like everyone else?
As to taking pictures of folks in full sun? Sorry but that is a sure recipe for racoon, squinting eyes, washed out (over exposed) colors... A flash just adds to the mayhem. If a family picture or a memento? Who cares.
If you lit a subject in the shadow and a bright background (like in the shade) an on camera flash camera is adequate as long as... The light does not kill the benefits of being in the shade by being too strong and/or by creating harsh shadows. Red eyes can become an issue too. Of course, you have flash accessories like the Wong system among many others.
A good CHEAP accessory for an on camera flash (integrated/pop-up) is... A semi transparent piece of tape. 'It is a professional thief light robber!!!'
As a bonus, if not removed it can play 'flash destroyer' is not removed when closing the pop-pup... You get two for one: A thief, a saboteur and Oh! Yeah! possibly three, a polluter!!!
Mitigating accessories for non-popup but on camera... On camera flash reflectors, black, white, silver, gold. If a flash has a wide angle adapter, that will control the light too...
If you have large reflectors with tripods and an assistant the last thing one would use is a flash on camera, just saying.
I am sorry, but I love the 'robbing life modifier'... (