It's cos it's some kinda pinko verse, that's why.
Off topic: This amusing article reports that when the verse was read to them, only 13% of Americans were able to correctly identify the Bible as the source of Proverbs 31:8-9. (80% of them also described themselves as "familiar with the Bible.") About a third had no idea where the verse might come from, and 54% named another source, Obama being the most common answer. Why am I posting this here? Because 3% attributed it to Bono.