"Which book did you file ___ [without reading ___]?"
Extracting from a subject might simply be too mentally taxing for the brain to process in real-time. Exceptions and "Parasitic" Gaps
Some researchers suggest the problem isn't grammar, but . Islands
"*Who did [a picture of ___] hang on the wall?" (The phrase is the subject). Why Do Islands Exist?
Modern theories suggest certain phrases are "phases" that become invisible to the rest of the sentence once completed. 2. The Information Structure View "Which book did you file ___ [without reading ___]
"Who did you see [a picture of ___]?" (The phrase is the object).
A occurs when the grammatical subject of a sentence acts as one of these barriers. In English, you can usually extract a word from the object of a sentence, but doing the same to the subject results in an ill-formed "island violation". Why Do Islands Exist
Subjects usually provide "old" information (the background). Trying to pull a "new" focus out of a backgrounded subject creates a mental clash.