Why are supports allowed to have stupid amounts of damage

This is my first discussion so please dont flame. So as the title says why do supports who have alot of utility also bring insane levels of damage? It doesnt seem fair to the adc that needs items to do any meaningful damage to also be beat out by someone who needs none. Take morgana and before you say dodge her q or any such nonsense we are just talking damage itself. Why when morgana get's her combo off that it does insane amounts of damage with effectively no items? If played proper the support can just outright just kill an adc and yet still have alot of utility so everyone else can follow up and potentially end fights. I cant think of how this is fair at all? I think you either do alot of damage with no utlity like cc or you get cc but have no damage.
It honestly getting to the point where any time I lose its not cause of the adc but the support who hard carries the game to victory making me wonder why i pick an adc instead of just another support in the first place. I know the one reason why adc are good is the reliable damage even when mana is gone and there ability to seige towers but does that really matter when you got so much utility that the other team just dies to the amount of cc? I don't think so. What do you guys think? Are supports just fine? Do you agree that they have too much damage for what they bring to the table? Let me know I would love to hear what you guys think.