Because even the best games ever need a polish every now and then.
As is the case with many popular games, Kirby's games also inspired some remakes. Some are just the same game but with a graphical update, others are re-inventions of the classic games. If Nintendo truly wants to capture the history of Kirby, these remakes may make appearances on the game collection:
Name: Kirby: Nightmare in Dream Land
System: Game Boy Advance
Release Date: December 2, 2002

What is it?
Kirby’s first foray on the Game Boy Advance came a year after the experimental Game Boy Color title, Kirby Tilt 'n' Tumble. Instead of following suit with another experimental Kirby game, HAL Laboratory instead opted to remake one of the series’ most notable releases, Kirby’s Adventure. An enhanced port, Kirby: Nightmare in Dreamland included improved graphics and power-ups, decreased difficulty, new sub-games, and the inclusion of four-player multiplayer.
Will it make the Kirby Collection?
It seems unlikely that Nightmare in Dreamland will be included in the collection, if only because of the fact that it is a handheld remake of a console title. It is much more likely that Kirby’s Adventure will be included in the collection; in fact, I would guarantee it.
Name: Kirby Super Star Ultra
System: Nintendo DS
Release Date: September 22, 2008

What is it?
One of Kirby's most beloved games gets a DS update, featuring brand new touch screen based mini-games and 3D FMV cutscenes while still retaining the original mini-games that made the original SNES release a classic of the era.
Will it make the Kirby Collection?
With the original SNES game being a more than likely candidate to appear on the collection due to its legacy in the franchise, featuring the DS would be redundant. Some of its ideas might make it in as separate mini-games, but chances are very low that this will appear in the final game.
Name: Kirby's Star Stacker
System: Super Famicom (Japan)
Release Date: February 1, 1998 (Japan)
What is it?
The classic block based puzzler makes its first appearance on the SNES.
Will it make the Kirby Collection?
The fact that this game was released exclusively in Japan (even if the Game Boy version was made available in North America) hinders its chances of being in the collection.