Swype used to (it still may, but I haven't been paying attention for a while) be pre-installed on a lot of phones. Until quite recently, only the beta- which was free through their website after signing up- was officially available as a stand-alone download. It's only been a few months since Swype was first offered through the Play Store, which marked the beginning of marketing directly to end users rather than phone manufacturers.
As B. Diddy notes, though, it's important to distinguish between Swype and swipe-enabled keyboards now, since that input method has been adopted much more widely over the past couple of years. You can swipe to input text using the stock Google keyboard nowadays, but that isn't Swype.