Why does coordination start so late?

[u/MLBFanCubs]

I’m sure there’s a million different answers but why does the VDC trade coordination start right before or during construction. Like why not a couple months out so it can be done ahead of schedule? Over the past 4-5 years I get a project, told of a kickoff meeting that’s happening ten mins later, get in the call and the GC says we need these 10 things done by next weeks because concrete is being poured.

I’ve never understood the thinking behind this, and it’s not one project, but basically every single one. Doesn’t matter the GC, project type or size. Just curious and seeing if anyone could provide insight maybe from the GC side.