I think American washer manufacturers were sort of tuned in with central hot water supplies as a given when designing modern appliances. If you will remember, CU threw a wet blanket on the idea of combos heating water, stating that while it might be a temporary, expensive solution to a shortage of hot water (perhaps because so many of the units with supplemental water heating were doing it with electricity) the better thing to do was to increase the supply of domestic hot water which was probably heated with gas. They did not put two and two together and realize the economy of point of use water heating in the machine nor did they stop and think that the two machines with the best washing ability were the KM and WP which held the timer from advancing until the water was at the right temperature. Unfortunately, the gas burner cone in these machines was located against the sump of the outer tub so there was a lot of water heating by conduction through the porcelain and that same heat was against the porcelain during the dry cycle with no water on the other side of it which resulted in the degradation of the porcelain which resulted in rust-through and the demise of the machine. Also, the gas combos were vented, which washers are not so they were set up to deal with the products of combustion which washers are not.

What I always did with my combos was wash and dry a load of colors first then, when the machine was hot from drying that load, wash a load requiring hot water which all of the hot porcelain kept hot.

I have thought of a mini recirculating heater on the scale of something like a hot tub heater with a pump moving water from the machine through the boiler and back to the washer but it would discharge the waste heat into the room which would not always be welcome. Integrating that with a washing machine's timer would present challenges and the liabilities of having something like this being controlled by the user presents far too many liabilities for any manufacturer.