If we all started to speak the same language, it would make most of the world's novels, short stories, poetry, song lyrics, and movie dialogue inaccessible, and different ways of looking at the world would be lost. And which language should be chosen? English, Mandarin Chinese, Spanish, Esperanto, or something else?

Ask bilingual speakers if they'd prefer just to speak one language and to forget the other one. Knowing two languages gives you access to two cultures, even if one is dying or dead.