From the US perspective, I have trouble understanding most of these.

> - it requires running more hot water lines / extensions, historically houses are built with lots of cold water lines but hot water lines only where required

Don't you need hot lines almost everywhere anyway? Every sink, bath, and shower has both cold and hot lines. So you're simply running two extra hots...one for the washer, one for the dishwasher. But usually dishwasher supply is run off the kitchen sink supply, so the "extra" hot line is just a couple feet. Actually, there's no cold line at all to our dishwashers, only the hot, come to think of it. So there's zero extra piping for the dishwasher in the US, and yes, one extra run for the washer.

> - for their heating requirement, a normal electric plug is more than sufficient in the land of 230V, this is is a similar issue to kettles basically

As other comments mentioned, the US does have 220V plugs for heavy appliances. It's already standard to have 220 in the laundry room and kitchen anyway - the dryer and oven use them. So this doesn't seem to explain the difference. It would be very easy run a 220 to your washer in the US, you'd need maybe two feet of cable and an outlet. Indeed, I don't know if it's code or not, but a lot of laundry rooms especially probably have the 120 outlet the washer uses actually wired up with four conductor cable, with the extra hot unused, because the cable for the dryer is right there next to it and why run the three conductor cable from elsewhere, when it's easier to use the four conductor. So they could literally just pop in the 220 outlet and be done with zero extra work instead, if washers were on 220.

> - they require an internal heater anyway as residential water circuits come nowhere near the high temperature cycles: 50-53C is common to avoid risks of scalding but some are set as low as 45, the standard high temp cycles for washing machines are 60 and 90, and dishwasher commonly have a heavy cycle around 65.

This is incorrect. My washer doesn't have any heating element. The dishwasher does to superheat the water, since at the maximum settings it boils water. (The steam cycle.) The thermistor is set during normal non-steam operation to run at around 130F/54C, which is the temperature of my water heater heater supply, but it's true that inlet temp is not guaranteed; different people will have different settings and the pipe run entails some heat loss. Plus it does need the heating element for the dry cycle.

> - it makes the machines more convoluted since they needs more inlets, a mixing valve, etc...

Dishwashers only have one inlet in the US. It's true that the washer has two, but it's not much more complexity. At least on mine, it just opens both valves at the same time, there is no "mixing valve." If you select hot it only opens the hot valve, warm opens both, and cold opens only the cold.

> - they're not really compatible with hot water tanks: you don't want your dishes or laundry to empty your shower water,

How are they "not really compatible" when it's bog standard? Your dishwasher uses a pretty minimal amount of water (mine fills with 1 gallon.) Washing machines use ~10-20 gallons. The standard hot water tank in the US is 50+ gallons. People do sometimes run out of hot water, but it's not from running the dishwasher at the same time.