[jps098]

It may be as simple as this: It's hard to pick up a date or meet new friends if you don't speak the language. The less you can communicate, the smaller your options, and the more of an outcast a person would be.

Just a thought.

[thefactor]

And perhaps those who do not learn the language are the product of a stricter household. If you are not allowed/not able to learn English, perhaps you are more likely not to be allowed to go out or mingle with others outside your family.