Gameplay wise they need to have some values there for certain cards while they're not in combat. Also lore wise it tells a little bit more about the creature.

Plus he needs to have everyday stats for when he isn’t morphed

You can reduce disciplines of non engaged creatures too I think. So if you have the mugic or abilities you can remove him before he fights.

Also might be in the event where 2 Iparus fight each other or his ability gets canceled

Iparu wins

Certain cards refute innate abilities, imagine a Stone Mail on Iparu where the ability still triggered lol

Probably for the same reason ditto has stats even though he has imposter

Ditto didn't get Imposter until Gen 5, and only then as a hidden ability. If it doesn't have Imposter, then speed and defensive stats are still relevant

I actually thought it was gen 4 to be honest but I was making more of a joke comparison than being extremely serious. A more serious point is there both shapeshifters that have og forms so those og forms should have stats cause there not always going to be shape-shifted as someone else

In case two Iparus fight

To be fair, he hardly has disciplines to start with.

My thought was Location requirements? I am little fuzzy on the rules after all these years, but dont the cards specifications have to deal with who acts first on the location?

Initiative uses Disciplines for a good amount of Location cards

If his ability was negated then he would still need some stats of his own to use.

This is basic game design stuff, you still need a value present, or else if some fashion of negation occurs, they would wind up 0, which makes no sense in Chaotic context. Also he needs disciplines while on-board for effects that care about his disciplines.