[dotancohen]

The issue is that a USB charger is not a USB power supply. A charger does its best, but makes no guarantee of constant power delivery or duty cycle. The power supply absolutely must provide its rated output at 100% duty cycle.

[SchemaLoad]

There's also the fact that devices would still need an internal PSU to convert the 28v USB-C to the multiple voltages that all the parts inside need. It would be smaller without the AC to DC conversion though.

[crote]

This is already the case today. Those mini pcs often take 19V, so it can use cheap and abundant laptop PSUs, which use that voltage for battery chemistry reasons.

Literally nothing inside it uses that voltage, so it'll just get downconverted to the single-digit voltages the chips actually need.