They should ALL use hot water. Most people have electricity and gas. Hot water is heated cheaply by gas, whereas having the machine heat it uses expensive electricity. Even more effective now that people have combi boilers so you don't need to have heated the tank before washing the clothes.
That was a really stupid design, how hard can it be to use only the hot until it senses it's too hot for the selected wash?
Mine is set at 30C, lower than that and it doesn't clean well at all. 40C would probably be even better. Enzymes are living things and like 37C presumably, just like you do.