My sister-in-law and my son-in-law COULD have done that
And they SHOULD have.
Had they spoken their native languages with their kids, I would have had two nephews fluent in Japanese and two grandsons fluent in Russian. Instead, I have one nephew who can read and write Arabic (learned in college) and four grandchildren who speak both German and English, same as our daughters. Because we raised our daughters bilingually, one of them now earns seven figures a year, a job she got because she was the only candidate who had that last qualification (total fluency in German and English) on top of the other candidates.
She didn’t earn that in the beginning, but within ten years, she did—a salary I’ll never touch in my lifetime, and I speak nine and a half languages (it helps that she’s also a workaholic genius).
Rather than get frustrated, when I’m frequently somewhere where everyone speaks a language I don’t speak, I say, don’t get mad, get fluent. It’s very rewarding to watch their jaws drop when they realize how busted they are 