Sometimes the resistance of the trace matters. I’m designing a motor controller that needs to carry 100 amps and the resistance of the copper means that large planes are needed to carry the current without overheating.
Beyond that I agree with everything you’re saying.
That's absolutely true, in power electronics there are applications where the current carrying capability of the traces really matters. Typically you'd either use a very wide trace or some other trick such as via'ing together multiple layers of traces or even to tin-plate the trace. In extreme cases I've seen traces reinforced with solid copper bars.
There is also extra thick copper clad board ('heavy copper PCBs').
