Often times companies invest in other companies for control. Let's look at an example. GM produces cars, which is a big process. Not only does it have to put together the car, but it needs to make each piece of the car. It may benefit GM to purchase seats for the car from another vendor. This would allow GM to focus on making the main parts of the car, for example the motor and electrical systems which is what they are known for. It could use its resources to research how to make the motor and electrical systems better and also send its employees to classes and training instead of using its resources to learn about making seats. If a company decides to do this and uses Company B to buy its seats, it wants to have some say on how Company B makes the seats. It wants to make sure that it uses a good material for the seat and that the seat will hold up in a crash. By investing in Company B it has some say in Company B's decisions regarding the seats rather then being at their mercy. Of course GM could always take its business