It’s probably a throwback to how arrays were separate objects in Clickteam products.
Also it does help keep things tidy to have the array actions and conditions grouped together. At least with how types are handled currently.
Construct classic actually had a way to assign arrays to variables, although they were pretty much constant. You couldn’t change the size or elements of it, and it wasn’t supported in all places. The feature didn’t make the jump to C2.
I think it would nice be have as a variable type though. If it made the array object obsolete I wouldn’t mind, as soon as you do something moderately complex that involves picking you realize containers don’t really help a lot.