There are probably countless reasons that make people working out.
Mental well being, energy boost, physical well-being, improving capacities to perform better in an other sport or changing the way they look.
Lifting weights is a particular physical activity that is probably linked to esthetic goals more than any other sport.
But is it for the good?
Changing the way your body looks
Being honest, we can't deny that 'looking good' is important to most of us. The image the mirror gives us back will impact our self-esteem and self confidence.
Everyone has his own definition of beauty, but I believe everyone is trying to look the best way possible.
Lifting weight is a particular sport where the main goal is to increase muscle mass (no matter the goal) which, after long enough, will change the way you look (the benefits of weights lifting).
If a lot of people use this sport to feel better in their body, there is also a part of them (more or less important) that is driven by the willing to improve the way they look. And there is nothing wrong about that.
Achieving a physical transformation is a very long process that requires a lot of dedication an investment. If you want results that last you will probably have to train for years. And that shows a lot of determination.
Wanting to change the way your body looks is fair. You are working hard for it and that is a proof of dedication and determination. You have the control on your diet and all the process is the fruit of physical and mental hard work. You can be proud.
However there will always be some work to do on self acceptance anyway.
Looking good is a good motivation but it is important to make the difference between changing your body and making it more muscular, and making it look the exact way you'd like to.
Everyone's body is different in many different ways. You do not decide your strengths and flaws and so you can't decide to have X's chest with Y's legs.
When you lift weights you improve your general health, and you increase your muscle mass. If you have a well balanced program you will increase all aspects of your fitness (5 reasons to hire a Private Personal Trainer).
It is not because you follow someone's program that you will look the same as them. It does not work that way.
You have different natural capacities with different weaknesses and different strengths.
Improve your performances
Wanting to improve the aspect your body looks is a fair goal but if it is the only one you might be disappointed at some point.
As said before you can not decide the exact way you will look.
Having goals that are measurable is important to keep a high level of motivation (how to make sure you improve).
You do not always see your progress in the mirror but numbers will help you monitor them.
Your body needs to be constantly challenged to improve and having a performance goal will bring some extra motivation that will have a double impact: keep on increasing your muscle mass (and so change the way you look) and help you see your improvement.