I think Kirby games are easy to make. For the 2D platformers they can make them quickly, without spending much, and they sell enough to make a decent profit almost guaranteed. Also, Kirby is a very "versatile" character, like Mario, and so any new gameplay ideas someone has, if not used in a Mario game, often they can and have built Kirby games around new gameplay hooks and nobody bats an eye. If it were "Star Fox Canvas Curse" or "Link Mass Attack" people would probably feel like it wasn't a very good fit. But Kirby is flexible for many types of gameplay. He also appeals to that family audience that Nintendo knows is VERY important for their business.
Upcoming Games To Get
Definite: Kirby Star Allies (Switch), Mario Tennis Aces (Switch), Fire Emblem (Switch), Yoshi (Switch), Pokemon (Switch), Kingdom Hearts 3 (PS4), Monster Hunter World (PS4)
Considering: Fe (Switch), Donkey Kong Country Tropical Freeze (Switch), The World Ends With You (Switch), Ys VIII (Switch), Street Fighter V: Arcade Edition (PS4), Kingdom Hearts 2.8 Remix (PS4), The Last Guardian (PS4), Shadow of the Colossus HD (PS4), Anthem (PS4), Shenmue 3 (PS4), WiLD (PS4)
