i only just started playing the game today so i only asked to learn. i wasn't saying it's a waste of time or anything. it's obviously in there for a reason but so far it's not been any use to me.
Just watch one match from Grimmz, CDN, Shroud, or Anthony_kongphan and you'll see the uses.
You don't build permanent outposts (except maybe within the last few circles). You build temporary shelters to fortify your position, heal, revive a teammate, or even as bait to lure enemies to attack it. As well, you can craft to scale mountains to get the drop on unsuspecting enemies.
In a top 10 situation, you can build strong defenses on ledges that require the enemies to expose themselves to assault you. With favorable circle positions, you can nearly guarantee a win with smart building and proper sniping.
edit: most of my structures in the early game are simply a wall and a ramp to peak and snipe from if i see an enemy in front of us with no flanking option