For very young children there is so much more to learn than just the abc's, counting, colors, and shapes. They're learning all day long. You can do a lot at home, but you have to leave the house to go to the museum, library, park, playgroup, market, swimming, hiking. All the world is a learning experience when you're a toddler or a preschooler. Some families are already homeschooling and for them homeschooling for preschool is a natural extension of what they're already doing with older kids.
Some families homeschool for preschool as a way to test the waters.
That is the case in our family. The decision to homeschool after kindergarten is not one to be taken lightly, but for preschool there's not much you can do wrong. In some instances homeschooling for preschool can alleviate familial pressure to conform and to send the children to a public or private school. Toddlers and preschoolers are endlessly inquisitive and they thrive with one on one attention. As your child grows, as you feed that inborn thirst for knowledge and let him progress at his own pace, you will see the results of your homeschooling effort.