They aren't well known, but they're an international standard. Getting everyone to switch to a new system will take a huge effort. As others said above, there are just so many symbols that I dare to claim it is impossible to come up with a symbol set that is self explanatory, or easy to memorize. As soon as you're in doubt about any symbol, you'd have to look it up, and then it doesn't matter whether you need to look up one or three.

I only know the one for temperature, the "no dryer" one, "wash by hand" and "no spin-dry". But like you, I don't give a shit. I wash everything at 60 (underwear, bed sheets, towels) or 40 (everything else) °C with spin-dry at 1400rpm.[*] Some pieces might wear faster, but so be it. I guess the vast majority of people does it that way.

[*] Ok ok, except wool or cashmere, or a suit. But this is something I just learned from my mom at young age, not by researching any symbols.