Because our heroes won't be who they are without their respective mentor.
I tried some humanised versions of these characters (except AkuAku, who remains in his mask appearance) for my CBNS project. Some of them will have a little role, more or less important, others will be mentioned in flashbacks etc...
Here's a quick introduction for each of them, and their relationship with our heroes.
(from the top to the bottom ~)
Betilla: great fairy from the Glade of Dreams, and Gardian of Knowledge and Learning. She guided Rayman in his journey to get back the Great Protoon, stolen by Mr Dark.
Big Face: a Mudokon shaman who saved Abe after he escaped from Rupture Farms. He is the one who granted Abe the power to turn into the Shrykull, the Mudokon Deity, after he successfully passed both Paramonia and Scrabania's trials.
King Rufus: Small by his height, big by his heart. Leader of the Gobbo people, King Rufus found Croc while he was still a baby. He raised him like his own son, and taught him everything about Gobbos's way of life.
Grandpa: Elder of the Wind Village Breezegale, Grandpa was Klonoa's grand father. Having a great wisdom and knowledge, he taught Klonoa everything about the History and legends of Phantomile.
Aku Aku: the spirit of a witch doctor inside a magic mask. Aku Aku has been found by both Crash and Coco when these two landed on the N.Sanity Island. Since then, he accompanies them in their journey and protect them as much as possible.
Nestor: being one of the five main leaders of the Dragon Realms, Nestor is also Spyro's main tutor. He was in charge to teach Spyro everything which deals with the art of pyromancy, both academic and practical.
Chop Chop Master Onion (aka Tamanegi Sensei): Parappa's main teacher, Master Onion is the ruler of the Fruit Dojo. He taught Parappa how to fight, after the latter wanted to be a hero.
Alfred: Who said elderly couldn't handle technology ? Retired secret agent, Alfred is now Gex' butler. From the Mission Control, he supervise Gex's trainings and missions in the Media Dimension. He can interact with Gex by way of holograms of himself, which enable him to be omnipresent to give him some useful pieces of advice.
Lack of new stuffs, sorry about that X(. My job is quite demanding these days...