Have you bothered to consider where your heart is? Are you training because you love it or at least because you want it or are you doing it for someone else? I think this is an important distinction and not many people bother to make the distinction. I see people who train because their doctor says they need to lose weight. I've seen people who train because their spouse is worried about them. I have seen people who train because they want to do it. The first two never listen to advice while the third can never get enough advice.
Where Is Your Heart?
For me I do this because I love it. I devour information about bodybuilding like it is candy. I get excited to try new techniques that I learn. I have an urge to hit the gym. It is amazing really. I would go so far as to say that I am addicted to training and that it makes me feel better.
Why Should You Do It?
Training is something that you need to be consistent with. This is why you need to do it for yourself. You can't do it because of someone else's desire for you. That will just result in you making excuses to skip workouts. Ultimately you will sabotage your own efforts.
Do this because you want it. Do it because you love it. Learn about bodybuilding by reading everything you can find. It will change your attitude for the better and the time you spend in the gym will become much more useful.
Why You Must Do It?
Weight training is essential for a healthy body. You can do all the cardio you want, but if you don't include weight training you will not reap maximum benefits from it. Get under the iron and lift. Hit it hard. Don't ever let someone ask if you even lift. Make it clear from how you look that you train.