They can't. They don't see those things as useful. Almost every homeschooling family I've known belongs to a fundie Xtian religion. An exception is our neighbor's daughter, who home-schooled her two kids until h.s. They did fairly well in h.s. In fact, the daughter attended Michigan State for a couple of years, then changed paths. The son works in construction. They're both great kids who are still finding themselves.
For most of the religious homeschoolers, the intent is to keep their kids focused on Bible and religious stuff; learning to read and write is just a means to that end. They really fear that if the kids are exposed to the real world, that they'll discover most of what they've been taught at church and by the parents is seen as superstition and myth, rather than reality.
Makes sense. I would think less than one percent of parents are qualified to competently teach trigonometry, Spanish or French, Shakespeare, and chemistry.
Maybe even less than one percent in the depths of MAGA world.