[cFyrute]

It's not a terrible mistake. A terrible mistake would have been having such power available on ports that even a reasonable person might short out by innocently connecting a USB C cable between them.

A couple 5.1k resistors add about $0.00001 to the BOM cost. The terrible mistake is on the designers of devices who try to forego these.

[willis936]

It's really not the BOM cost that drives these decisions but the assembly cost of adding placements. Time on the assembly line is very valuable and doesn't have a simple / clean representation on a spreadsheet. It's dependent on the market and right now assembly line time is worth a lot.

[f1shy]

That is exactly the reality. I work in a place where we build HW. The resistor costs almost nothing. But installing it, having it in stock, making sure the quality of yet another component is correct, eventually managing another vendor, all costs. So much, that the cost of a resistor we put a value of some cents (up to ten) even when the part itself cost so little that the software has problems tracking it.

[derkades]

Except that connecting 5V to 5V does not cause a short circuit. No current will flow without a voltage difference. If there is a difference, the capacitors in one of the power supplies will charge up to the same voltage and then current stops flowing again.

[zettabomb]

That would be true if both sides were exactly 5.0V, but they're not. There's a 5% tolerance, from 4.75V to 5.25V, and in practice you will see chargers often run "5V" at 5.1V intentionally, to account for resistive loss in the charging cable. If you accidentally connect your "5V" device to the host's "5V" you may find that the host simply disables the port, which has happened to me more than once. So no, you can't just blindly connect them together.