So did Google? Not trying to be trite here, but that's essentially exactly the point. They didn't want to let a sketchy charger brick the phone, so they disallowed sketchy chargers.
You could say that the phone should try to accept any charge and never break, but that's a nontrivial amount of electrical-engineering and expense involved in accepting basically any wattage/voltage that a sketchy charger may produce.
Not to mention that the sketchy charger can brick the phone now. The phone can just regulate its own power supply and charge however it likes, all the charger does is supply current to the coil.
You could say that the phone should try to accept any charge and never break, but that's a nontrivial amount of electrical-engineering and expense involved in accepting basically any wattage/voltage that a sketchy charger may produce.