For me the biggest problem with laundry symbols is that they're often printed so small that after a few washes they become too blurry to recognize. Also, while I can feel with my hand whether water is "cold," "warm," or "hot." I honestly have no idea what the actual temperature of the water in my washer is in degrees Celsius. Furthermore, I live in the US (which is not where any of my clothes are made), so there's th…
The explicit temperatures are for machine washing, don't you just... set the washing temperature to whatever you want?
If you're washing by hand, it's unlikely that you're washing above 40C, and that's if you like hurting yourself: at 50C (120F) serious burns take about 10mn, at 60C (140F) it's around 3 seconds.