Why are some weird Wikipedia pages yanked into oblivion?

In a single day, about 500,000 edits are made to the English version of Wikipedia, and approximately 800 new articles crop up. But for each incoming new page, anywhere from 400–500 pages are deleted entirely, daily. “Famous watermelons,” “How do i stop my son from looking at picachu porn,” “List of fictional characters with removable or interchangeable heads” — all have met their fate in the digital graveyard of Wikipedia’s “Deleted art