Not entirely true. Quite a few phones these days come with a 'standard' charger that's rated at 5V 1A or 1.5A or whatever and the phone will only draw that. But, they may support Qualcomm Quickcharge standards despite the phone only coming with a basic 5V USB charger. Quickcharge bumps the voltage up to as much as 20V and current to 3A if you have a compatible charger.