Wind In Ground (WIG), is an old concept.
In short: Wing-tip vortices create an additional drag on the aircraft known as the induced drag. However, when the flying craft (or bird) flies close to the ground or water, these vortices don't get enough space to develop which results in additional lift and reduced drag. This phenomenon has been effectively used in transportation vehicles to create ground effect or WIG crafts.
Although a paper titled 'Wing-in-ground effect vehicles' declares that many technical difficulties have either been solved or can be solved, according to this wiki article, there are some practical issues in using these crafts for regular passenger traffic.
Since hovercrafts also glide on air cushion, and yet they are not that rare, what makes WIG so uncommon? (Analogy wise, hovercraft is like helicopter while WIGcraft is like airplane)
Is it the engineering aspects that makes them uncommon? If yes, which aspects?