When Kirby absorbs Sora and then uses his Magic, it is immediately clear that Kirby does not get a Keyblade of his own. Instead, Kirby uses an ethereal glowing weapon that resembles a keyblade but is entirely made out of light and sparkles that changes color depending on the spell. While this can be interpreted as being a restriction by Disney over the Keyblade's imagery, Masahiro Sakurai on Twitter chalked it up to being done for lore reasons as he said "...only Keyblade Wielders can use Keyblades..." implying that Kirby isn't "chosen" as barer of one and thus has to use the three spells differently.