I think the "distributed across the map" part is key. In beginner / intermediate play, a really key ability is to actually remember to keep building stuff while scouting or fighting. Can you throw down that building on time while also looking at your opponent's base and gleaning useful information there in an early scout? In an early skirmish, can you micro well enough to gain a minor advantage while also still building workers for the long term economy that actually matters? In the midgame, it's worse, you have building workers, troops, scouting, managing supply, map positioning, upgrades, watching the mini-map for counters/drops, etc, etc, etc all going on at the same time in different places of the map and screen.
90% of the players in the world can't really do these things consistently well because the require you to take care of a lot of background work while actively focused on the exciting stuff. That's genuinely hard and you get better at it incrementally at best.