There are plenty of reasons to use elliptical trainers for workouts even though I admit that I do not use them often. A significant reason is I do not go to the gym that often due to time constraints. I do most of my workouts without equipment and outdoors.
Less Pounding on Joints
Training on the elliptical has little to no pounding while running applies a lot of force through your legs.
A study completed by the University of Missouri-Columbia looked at oxygen retention, lactic acid build-up, heart and perceived exertion between elliptical trainers and treadmills. What the study found was that the physiological response between the two was nearly identical.
Therefore, you aren't losing much even if you are using the elliptical in place of running.
Strengthen the Quadriceps
More often people tend to have stronger quadriceps versus hamstrings. However, if your quads require some serious work, then the elliptical may be a great aide in strengthening them. The elliptical machine produces superb use of the quadriceps. Plus, a study completed by Willamette University found that if you peddle backward on an elliptical that you gain even more use of the quads.
May help if you are a runner suffering from weak gluteus maximus or vastus lateralis
Elliptical Trainers are well known to make more use out of the butt muscles and outer hip muscles. Therefore, if these muscles of yours need work then passing up a run on the treadmill for a bit of work on the elliptical may be more helpful.
These are my top three reasons for using an elliptical trainer. I admit I don't use the elliptical much because I'd rather be outside running. However, if the weather is bad or something else is keeping me inside the elliptical is a great alternative to a treadmill or even a bike.