I always have doubt on this method

Or so called pre pre education. Is it really necessary to teach a toddler to read? My grandma was illiterate so she couldn't read or write. My grandfather was too busy to teach his kids or play with them, joining so called 'revolution'. The environment was rough, eight years of war time, children didn't have time to playdate.

But my dad graduated from the best engineering school, the famous T University in China in the 1960's, and all his brothers had college education. I'm pretty sure nobody had taught them how to read a book before formal schooling. Not even bedtime story reading was possible to them. So how could these kids grow up as normal, intelligent beings?