Questions?

[Reijin]

Ok, from what I remember, going on sheer memory... The reason that certain Digimon digivolve on their own without a digivice is due to generating a specific amount of energy within their body. They could, if they ate enough food, digivolve a level for it. But its like they have to actually grow with it, so they can't naturally digivolve to a massive level without a lot of power.

So certain ones would stay in a level due to basically having a routine going. The digidestined ones would revert to Rookie due to the fact that they had a very non-routine style going, and would eat a lot but also consume a LOT of their energy on a regular basis, which is why some of them would revert to their Training state sometimes.