One of the biggest stumbling blocks to starting and sticking with a fitness program is lack of confidence in one's own ability to exercise correctly and effectively. Confidence comes with knowledge. As fitness professionals, it is our responsibility to educate clients so that they never again lack the knowledge or confidence they need to continue an exercise regimen, with or without a trainer, for the rest of their lives.
The principle of progression in fitness says that in order to improve, one must work at levels that are higher than what is considered "normal". Most people find it difficult to push themselves beyond their comfort zones. A trainer provides external motivation to work at levels of intensity that might not be achieved alone.
Many have gym memberships, but few actually get there on a regular basis. It's amazing how much more likely people are to workout when they have an appointment. A trainer provides the structure and direction needed to help get you going and keep you on track....all you have to do is show up!