The “normal” way to support 25W would be to support 9V 3A input, giving 27W adapters functionality. Or possibly accept multiple options such as 9, 12, and 15, a

The “normal” way to support 25W would be to support 9V 3A input, giving 27W adapters functionality. Or possibly accept multiple options such as 9, 12, and 15, and then buck any of those down to the system voltage needed. The 5V5A is because raspberry pi org is being cheap/lazy and doesn’t want to design or pay for a power converter to handle that on the pi, and instead is pushing that complexity/cost to the user via an overpriced and nonstandard supply.