Why didn't Type-Null have any role in the story?

Its whole back story is revealed in that one room in aether foundation. All type null has to do with the story is that its what gave gladion a reason to run away

Because not everything should just get dumped on you.

You can find out what's up with Null through piecing together the bits yourself. It's probably better that way since Gladion isn't a constant enough presence that you can care about Null.

>>30315956
Type-null had exactly the same role as Cosmog without any story development.

>Hi anon here have a free Type-Null
>There's a more of them lying around that I didn't bother to rescue before and I thought you might want one

He's just Gladions doggo

>>30315912
Wait for Gen 4 remakes/sequels.

>>30316085
They could've given him an Absol or Umbreon and the story would've been identical apart from a few lines of text

Just a pre evo to a poor man's
arceus.

Same could be asked for the Ultra Beasts

>>30316078
There were only three type null ever made, one that Gladion has and evolved, one that you were given and one that is unknown (Possibly/Probably dead after going on a rampage, unless Gladion has this one)