[namelosw]

> If tones were completely irrelevant regarding understandably then they would have disappeared long ago.

Probably because it's a legacy and disappearing slowly? Modern Mandarin only has four tones left and has already lost tone patterns.

Do you know there's a "robot tone" in Chinese? It's simply swap every character to the flat or the first tone. Though it's under the stereotypical false assumption that robots have troubles with tones, kids in the late last century often communicated in that tone for fun without issues.

At the end of the day, vocal Chinese is always ambiguous with or without tones and in practice heavily relies on context. It requires written language to truly fix that.