What is the point of free practice? It is to prepare bike, rider, and team (not necessarily in that order) for Sunday's race. On a good weekend, you spend Friday testing your base setup and getting an idea of which tires to use. On Saturday, you refine the setup and check how your preferred tire lasts over something approaching race distance. In warm up on Sunday morning, you might try a final tweak in search of more tire life or a fraction more performance.
The goal of all this is simple: to arrive on the grid on Sunday afternoon with the best possible setup. To eliminate as many unknowns as possible, and provide the rider with the sharpest possible weapon with which to do battle. From that point on, it is up to the rider.
That's the theory. In practice, of course, it rarely runs quite that smoothly. There is always something cropping up that makes the whole process a good deal more complicated than anyone hoped, unexpected obstacles to be overcome along the way.