Robots are far from mainstream. Why should anyone consider robot makers as an investment? It's true that robotics is a niche market at present. Industrial robotics has been a steady $5 billion industry but service robotics has been rapidly increasing and is estimated to hit $20 billion by 2020. Combined with an estimated $10 billion for industrial robots, that takes it from niche to a new status.
Microsoft's Xbox Kinect device is a good example of an unintended consequence helping the robotics industry by radically cutting costs for vision systems. iPads and tablets are another example helping cut the learning curve by using familiar devices as front-end controllers. Hence the need to pay attention and track the progress of all that is robotics-related. An investor doesn't want to be left behind when the market takes off.