Perhaps they do speak English well enough to go shopping etc but not enough to describe the complexities of different types of pain in different body parts. Someone's might be able to say that I have a pain in my arm but it's the type and history that will say whether that's because they've been stung, they've sprained a muscle, they've torn a tendon, they've broken it or they're about to have a heart attack. The cost of correcting a wrong diagnosis might be far more than the price of a translator.

Perhaps it should be more about how the cost of translating could be reduced? By employing more people who speak other languages fluently who can be called in if there's an emergency? By encouraging staff in hospitals where other languages are needed to try to learn them - perhaps with a good work bonus if they do so?

Incidentally, what's to say that their husband/wife/children aren't hardworking English-speaking taxpayers and the poor patient just doesn't have much a gift for language?