Learning to free dive first allows the diver to become accustomed to the underwater environment and the use of basic fins, mask and snorkel. If one masters basic snorkeling skills such as clearing a flooded mask, efficient finning techniques and the like, and becomes comfortable in the water, then getting SCUBA certified is a piece of cake.
Personally, I would recommend that anyone wanting to learn to dive should take up snorkeling first and learn to use fins, mask and snorkel. A good set of snorkel gear can be had for less than $100 and you can learn on your own, at your own pace. Snorkeling is fun and easy and there are plenty of good books out there from which you can learn snorkeling techniques. Then, when swimming underwater has become second nature, sign up for a SCUBA course.
Mastering snorkeling first helps gain confidence and skill. IMHO, the best SCUBA divers are accomplished snorkelers with tanks on their backs.