This is major RTS gamer brain. In those games, the scarce resources are the raw materials, because it's more dramatic to send your harvesters into the unknown to be attacked by enemies, while the actual knowhow on how to build stuff is passively "researched". So if you need to build a bridge, you magically have the planners and the engineeers and the building crew ready and waiting, but they need steel and stone to start, which you never have, because you just panic-built a bunker to defend your base.

In the real world, getting enough steel to build a bridge is easy enough - I imagine the lead time to be a couple months. Actually finding a team able to plan and construct one is another matter.