I only hope those expats are ready to pick up and move either back home or to another country because they can't find a job in English in their country. They might be fine though. However, I'm being serious and am not joking, because it was my own concern. I am probably ok though as a software developer, maybe, but the thought of picking up and leaving at this point is really tough. At the very least, securing my assets and collected pension is well worth the time I am putting in to learning a language. Hey - you even get brownie points when you can mutter something in the local language.
As an example, here in Norway, I have read of expats, specifically British expats, being denied various earned benefits because their residency permits have expired and/or they decided to return back to where they came from. The collected pensions were not afforded to them. IANAL definitely, so if this is ok or not in terms of EEA rulings is maybe another story, but this, even being pre-Brexit, was still worrisome to me. At the time, years ago, I was not a citizen here nor a citizen of the EU/EEA, so tying my wife and my benefits' fates to whatever employment we were able to attain is a bit concerning. Not being explicitly tied to employment and maintaining the full rights of every other citizen by being one myself is a relief. Of course, one of the requirements was reaching a certain language level (it was A2 when I got it, which I aimed for specifically, but the government has since decided to push it up to B1.)
Also, I don't have children, but I have had co-workers who do, who sought to learn enough to be involved their children's education and also really can't afford expensive international schools. I mean, we all make salaries that are average to our profession, citizens and non-citizens alike; I mean, if you want your children to only speak English, work in a English-speaking country.