Think of it:
If you're from non-english speaking country, then you'll be spending like 14 years at school learning english.
Additionally you'll have to put a lot of effort outside the classes and you'll still be at probably good / very good, but not native level.
So, in order to compete with engineers, scientists, etc from english-first countries you not only have to be as good as they are, but all of that while paying this "english-learning tax"
It is like a few thousands of hours of effort required to get decent results and now think about it how many other things you could spend that time on.
It is actually crazy when you think about this. Almost every person in majority of countries needs to pay that huge penalty that's required to enter science, business, international world.