This is good for rehabilitating an injury or strengthening a specific body part. Machines can offer high-tech options like varying resistance during the lifting motion. This can tax muscles in ways that a traditional barbell cannot. Changing the resistance on a machine simply means inserting a pin or entering a code. With free weights, plates must be hoisted on and off the bar.
Machines are self-contained and neat.
There are no weights scattered about creating a hazard and an eyesore. In general, machines may be preferable for the novice because of their convenience, safety, and ease of operation. But cost is a factor for home exercisers. Strength athletes prefer free weights to machines, because they yield more sports-specific gains. Beginners may want to eventually add some free weight exercises to their routine to cover all the bases.