You're Not Seeing Results
You Don't Know Where to Start
You're Bored with the Same Old Workouts
You Need to Be Challenged
You Want to Learn How to Exercise on your Own
You Need Accountability and Motivation
You Have a Specific Illness, Injury or Condition
You're Training for a Sport or Event
You Want Supervision and Support During Workouts
You Want to Workout at Home
There are plenty of other reasons too but this is a good starting point...