When you have 10M+ documents, it takes a long time for a team of lawyers to review them. So a company with AI/ML is at a huge advantage in identifying the documents a lawyer needs to win a case.
To get accurate results, you need a lot of data, but to crunch that data you need a lot of power, not just speed. A lot of the processing is done now with GPUs (thousands of cores)...traditional computers are CPU intensive and have limited number of cores. Think for example a multi-threaded application running on GPUs vs CPUs...the GPU can divide the problem in more tasks and the processing can be done more accurately not just faster.
http://www.nvidia.com/object/what-is-gpu-computing.html
PS: I think people overuse "Artificial intelligence" we're no where close...but it excites people compared to "machine learning" or "deep learning" or "convolutional network" or just statistics...It's just trying to find an equation that fits the data like linear regression.