Even though they are able to live here without it.
Everyone in the world knows that English is the language spoken in the U.S. and most immigrants are prepared to learn it. But when they arrive, many of them (especially Spanish speaking) find signs and other information in their own language and quickly realize that they don't have to learn more than a few words of English.
It is completely understandable why they are reluctant to learn it. Learning a new language is hard, if people don't have to do it, they probably won't. But these people also won't ever be fully integrated into our society. In the past, the first thing new immigrants did was learn English. They had to know English to work and drive and shop. When everyone in the country speaks the same language, even with an accent, the country is much more united than ours is now.
Now they can live in their own little communities, watch TV, listen to the radio, read a newspaper, shop, work and even drive without speaking ANY English. They can get government forms in their own language and almost all offices and departments have interpreters available for them.
Many new residents know almost nothing about this country they live in. Without understanding the language, they don