I certainly do know why, it’s central to the whole one book of the bible. If you and other Catholic believers like being unknowledgeable in the scriptures, that is certainly your choice, however, the revelation from God is not difficult to understand, but you yourself must study it. You take the position that So and So will study it for me and then tell me what it says. If all your teachers can’t figure it out, then they certainly have no gifts from the HS.
Apparently the Ethiopian eunuch didn't think so. When Philip asked him, "Do you understand what you are reading?", the eunuch replied, "Well, how could I, unless someone guides me?"
If you were right, Philip shouldn't even have asked the question. And in reply to the eunuch's question, Philip should have rebuked the eunuch for failing [ironically!] to understand the perspicuity of Scripture. "You ignorant man of little faith. How can you possibly not understand what you are reading? By your ignorance and self-doubt you are setting an example that will lead future readers to think that they need someone to guide them as they interpret Scripture. Don't you know that you have the Holy Spirit to guide you? Even the fact that I must now rebuke you will be used by future believers to support your heretical notion of needing a guide. Carry on and (as I shouldn't have to tell you) say nothing of your lapse in faith in the Holy Spirit's guidance."
-A8