Why is it necessary to use the rules and exception framework when it can be done the way it has been learned originally and this is shown? Will this affect the way one answers?

After what has been taught so far, is it necessary to kick something up into the domain? Can one continue to gather the sufficient and necessary conditions as they were and negate them to still get the same results

Is there any way I could get a different example so I can better understand this? I find myself falling into the traps of confusing sufficiency for necessity the most.