Let’s take the case of a USC power supply. You build a transformer which converts, say, 100-240VAC to 5V, 5A. The minimum is 0.5A, so you want devices to know they can draw more power. Before USBC, the only USB voltage allowable was 5V, and only the amperage varied.
With “old” USB, you just supply the power to the power pins. You might tie in a resistor to help devices know they can draw more power.
With USBC, it’s a better standard because the discovery mechanism allows devices to handshake and pull up to 100 Watts at several different voltage levels. But you need silicon logic to do this, and that logic costs money. Period. That silicon can get cheap, but it has to be paid for.
Second, let’s look at a MacBook. Here it’s really simple to see: Those USBC ports are all bi-directional charging ports. You probably think that fifty cents or a dollar extra doesn’t matter in a $1,000-$2,000 computer, but it does. I can say for sure that adding ~100 Watts of charging power to three or four ports is very expensive, and it’s bi-direction to a lower Wattage, which is also very expensive. Those features simply aren’t present in older USB. Without getting into all the details of the BOMs for those power regulators, I can say it’s a certainty that lower end laptops will not have power on all their USBC ports, they’ll have a power icon over just one.