> because baths around 45-50 C (113-122 F) aren't uncommon at all in Japan
You are stretching it. Most hot onsen are above 40C but certainly not above 45 or close to 50. At 50 you feel like you are boiling. And even if the source is at 45 C you never sit right next to the source, a few meters away the temperature loses several degrees.
ANd people in Japan don't go to onsen every single day either. At home the usual temperature is rather 40~41.
You are stretching it. Most hot onsen are above 40C but certainly not above 45 or close to 50. At 50 you feel like you are boiling. And even if the source is at 45 C you never sit right next to the source, a few meters away the temperature loses several degrees.
ANd people in Japan don't go to onsen every single day either. At home the usual temperature is rather 40~41.