Why is there less fixturing with 5-axis CNC machining?

The range of motion is achievable from the cutting head & extra rotational axes means that these machines can reach five sides of a part. For example, if a geometrically complex part were needed for aerospace, a five-axis CNC machine would be the most capable machine to achieve this. This is due to its ability to reach complex angles and cut areas hard to get, such as a compound curve.