The official Swype is avialable in more places than just Android,
http://www.swype.com/category/get-swype/. In some cases, like iOS, the developer of the OS doesn't allow for it, no matter how much Swype might want to be there. In other cases, various other Swype type of clones are also available on different platforms.
The point is that it is a feature that is more than a gimmick and is of use to quite a few of those who try it out. No one has to use it, and no one's default experience will somehow become worse if the Swype option is there and they simply decide not to use it. Just like T9 in the days of feature phones, most people used it and liked it, but many people would just use regular "Abc" method if they wanted to and didn't really complain about T9 also being available.