But why not just build a mass driver, then? It's a somewhat large horizontal structure, compared to a space elevator which is an absolutely humongous vertical structure. If you can reach 2 km/s on magnetic rails, you don't need anything else to launch from the Moon -- or even land on it.
Because unless you reach escape velocity, you still need to adjust your trajectory to insert into orbit, or else you're just going to crash back on the surface.
If you use a rocket that's fine you just point in a different direction and burn, but if you're trying to launch, say, a few trillion tons of stuff, you need something a tad more efficient
It's not like you need no maneuvering when you use a space elevator. At some point you have to detach from it. You'll always need course corrections afterwards.
