There is speculation that the plane was deliberately diverged from its route because if it was only an accident the plane would have sent a distress call but pilots did not call any emergency services. Secondly, the Malaysian airport authorities tried to contact the plane after it went missing from radars to no avail something which suggests that the plane communication systems were deliberately switched off. What adds to the belief that the plane was deliberately sent offcourse is that the last plane pings came far from its intended route.
The reasons for pilots decision to cause such a disaster by killing themselves and hundreds of passengers and c rew is not yet clear.
Now about your question that why after one year since the disaster happened modern science and technology have not helped locate the plane,let us consider one thing. The plane went missing over a vast expans e of the sea. When the plane's batteries died down it means it could not ping any more. With no more pinging this meant that the aircraft search was now made more difficult because the last signal was no more. So the search efforts now depended on sheer luck. It is like searching for a lost sewing needle on a football field without knowledge about the exact location were it was dropped. It can take months or years to get it. So, modern technology still has a long way to go in order to overcome some challenges we are forced to face.