To or Not to Have a Dream

We all have dreams.
Since we were kids, we are all taught by our parents, teachers, or family to have a dream, so that we have something to hold on, something to achieve. Some are lucky enough to have a chance to work on their dreams on their own way, and turn them into reality.

A girl named Lana loved singing. She was a great singer with amazing voice. There were so many unwritten songs that could be sung perfectly by her. Someday, he married a guy and had kids, since then she wasn't able to continue singing.

A girl named Luna loved dancing. She was very talented as a dancer while she was young. There was so much to explore on her talent. Someday, her parents told her to stop because they believe dancing might led to some unhealthy midnight life.

A girl named Lina loved painting.She effortlessly created wonderful paintings with her hands. She always put her heart on the painting. Someday, she was offered by other career opportunity and everybody told her to take the job and leave the paintings behind.

They all had dreams. They all had something they love and would work their ass of on it. They all had something they could really put their heart on.

The thing is,
I never really understand..
Why we (especially women) are taught to have a dream while at the end when we grow up we are asked to give it up?

Why can't people let others live their own dreams?