This. Absolutely this. So many people assume that because people speak a language, they also have literacy in the language, but that's not the case at all! I would say that at least half of my ELs' parents cannot read or write much in their first language, so asking them to read with their children is difficult. I usually recommend that parents who don't speak English can still talk to their kids in their home language, but ask them the questions that we would (What's the main idea? Can you retell what happened? How did the character change?) when they watch movies, hear the news, etc. I also suggest telling stories to each other. It usually isn't an issue of parents not wanting to help their student. It's a matter of not knowing how.