Personal Trainers have many roles, some personal trainers work with people to make their clients lives better. Others are sometime gloried gym instructors looking to earn more money. Gloried gym instructors will, not be able to adapt sessions when you turn up with injuries or problems. Where as a real personal trainer can adapt in minutes to situations that occur during a session.
A real personal trainer will look and listen to the goals of a client. They don't try and force, their skills on their clients. This is because they know, if the client does what the trainer asks, they will get the client their results. This is because a personal trainer works out how long they will be working with the client, so when they reach the last two months with the client they can try and find a new client to replace the lost income. A good personal trainer will be able to tell you where you will be in ? months time. This happens by understanding the bodies adaptations to exercise, live cardio vascular improvements each week and strength increases.
A glorified gym instructor will not be able to tell you this and will make up goals for you to help earn more money from you, rather than a real personal trainer, looking after you and wanting to to achieve your goals. The satisfaction a personal trainer gets from helping a client achieve the goals they set, can not be express, or matched by financial gains.