DSS was 8 and struggling to get over his mental block of reading a chapter book. You know that block that says, "WOW THAT BOOK LOOKS TOO BIG!!" So rather than choosing to read it, which he was more than capable of, he would grab little golden books and Dr. Suess. Now, I had no trouble with him reading for pleasure, but I DID have trouble with him limiting himself to small children's books out of fear. So yes, I did push him and require him to pick out chapter books which, once I got him to start reading them, I couldn't get him to slow down.
DS is 9 now. At 5 he was reading reference books, we had a limited supply of the type of book he wanted. So we would go to the library. Problem was, he was obsessed with dinosaurs, he has been since before he was a year old. He would ONLY pick reference books about dinosaurs. So once again, when he got to be about 7 and had read these books through and refused to read anything that wasn't based on dinosaurs I DID force him to pick out a fiction book. Once he read one, he loved the series and now he is such an avid reader that I have trouble keeping enough books around for him to read.
DD is 7 and isn't reading well. She has trouble with it. She will pick out only books with pretty pretty pictures of princesses and ponies and then demand that they be read to her. Well, why am I going to read her a book full of facts and information about ponies if she isn't willing to at least attempt to read a book that is at her level? So yes, I demand that she picks out at least one book for HER to read. THEN I will allow her to pick out a book for me to read to her.
Every family situation is different and you never know what their reasons are for making those decisions. You may not agree with them, just as you may not agree with my reasons, but they are reasons, and well thought out reasons that I contemplated for a long time before implementing. Now, for dss who is 13 and ds who is 9, I let them go get whatever they want. For dd, we are still working on it. But, once they get past whatever trouble spot they are in, I no longer feel the need to control that area. Dss's issue lasted for about 2 months. Ds's issue, once I decided to deal with it, lasted about 2 weeks. DD has been having this issue for about a year now. Each one is different. I am actually hoping that with ds who is 4, won't have any issues and I won't have to control that issue at all.