The way one designs hardware in is to optimize for the most common usage scenario with enough capacity to account for the peak use scenario (and with some safety margin on top).

However specifically for power sources, if you want to handle more power you have to for example use larger capacitors and switching MOSFETs, and those have more leakage hence more baseline losses. Mind you, using more expensive components one can get higher power stuff will less leakage, but that’s not going to happen outside specialist power supplies which are specifically designed for high-peak use AND low baseline power consumption, and I’m not even sure if there’s a genuine use case for such a design that justifies paying the extra cost for high-power low-leakage components.