> Why does it always have to be an accident?

Because that's a surprisingly common way for things to be discovered.

Saccharine? Somebody working in a lab didn't clean their hands well, licked their fingers, and discovered it was sweet.

Aspartame? Somebody working in a lab didn't clean their hands well, licked their fingers, and discovered it was sweet.

I think this is true of basically every major artificial sweetener except invert sugar.