There is a lot of work going on to develop 3D printing as a mass manufacturing process. It is improving rapidly, but you have to understand that in the physical world progress is always slower than in software. 3D printing isn't a small change in manufacturing process (like more advanced CNC machining is) but a completely different approach. The level of investment, testing and iterating required to produce 3D printed components which demonstrate proven reliability and lower costs than existing processes is high.

The aerospace industry are actively pursuing 3D printing as a manufacturing process. Selective laser sintering allows shape-optimised parts to be built out of titanium - something that we cannot do any other way - which will lead to upwards of 50% weight savings. It will make a huge difference in the weight (and so efficiency) of aircraft. The issue is that the aerospace industry operates on the principal of proven heritage. The 787 may be the newest large airliner, but there's nothing in it that we haven't been using elsewhere for 20 years. Space is even slower at adopting new technologies - reliability is key.