Rumor has it that in 1950 Dr. Seuss heard a three-year-old kid recite, from memory, his 1948 Thidwick the Big-Hearted Moose. Yowza. Even more impressive when you remember that back in those days, kids weren't supposed to be reading until they were six or seven. Seusspert Charles Cohen argues that this little incident proved that younger kids could be reading, too (source). And that's what supposedly convinced Seuss to stick to rhyming. Rhyming seemed to be the key (the key, you see!)—the magic formula for teaching very young bibliophiles to read.
The formula was honed to a science in 1957 with The Cat in the Hat, a book specifically intended to take over the world. Or at least reading classrooms everywhere (source). It was a stunning success (duh), but the formula needed perfecting. Seuss's answer? Green Eggs and Ham.
If we think of it that way, Sam's green eggs and ham take on a whole new meaning. Maybe these kooky books can be seen as fun, adventurous alternatives to the boring newspapers the big guy reads. (No offense to newspapers. Well, a little offense.)