I suspect washers with heaters come from places that original had cold water only.
The reality is we are overthinking it - "cold/warm/hot" is about all we need, and "warm" is really just "fill as fast as possible" often, since it opens both hoses.
Shocking as it will be to you -- I'm just realizing that this differs between US and rest of world -- a home washing machine in the US can only go as hot as what comes out of the faucets. It cannot wash at 90C water, and likely can't even do 60C water. It can only do as hot as the "hot" tap water, which depends on what the hot water heat is set at, which is usually somewhere between 120F (49C) and 140F (60C).
