Why is Sky Skipper so forgotten by Nintendo these days, other than occasional references to it within the Game Boy Camera accessory?
Look at its release history. The arcade game was released in 1981 but only in Japan, while the only home port was that of the Atari 2600 version (published by Parker Brothers, which was also the console/computer licensee of another Nintendo arcade game, Popeye), which ironically was only released here (the U.S.). I re-iterate: It's very ironic that a game released only in Japanese arcades would somehow find its way into American homes on another port.
I'd like to think its being forgotten is perhaps due to the continuing success of its first big arcade hit, Donkey Kong (also released in 1981). The enemies were all modeled on DK, and even one of the stage clear tunes is an extended version of DK's stage start tune ("How High Can You Get?"). Moreover, another stage clear tune was recycled for use as the second level clear tune for Donkey Kong, Jr. (when you complete the chains board every two rounds from Level 2).
You are a pilot, the aptly-named Mr. You! The gorillas have trapped the King and the royal family (Jack, Queen, diamonds, hearts, clubs, spades, in the forms of animals), and it's up to you to destroy the captors with your bombs and save the royal family.