As the friction is being reduced, the speed of the travelling object increases. However, why is friction important in formula one racing?
Depends on what friction you are referring to.
Aero friction is important because it determines how well the car slips through the air, as well as how well it plants itself to the ground (generally trading one for the other, although you can actually achieve both to a limited extent with aero devices that work only in the laminar layer of flow; but most of the effect one way or the other comes from wings and devices that work in the turbulent layer).
Friction in the engine and driveline are key to how well they operate. Less friction will mean less parasitic loss of power and less heat, which will improve performance. And though less heat will mean better reliability, often times it becomes a balance between the two as some methods of protection will increase resistance (if not actually friction).
Friction is also the key to mechanical grip on the cars. The tires are the only part of the car in contact with the racing surface, and thus they are often the key limiting factor on all performance. Tires obtain their grip through friction. With zero friction here, the car would be unable to propel itself forwar (or brake or turn or anything else).