As my favorite money blogger, Trent Hamm (The Simple Dollar), says things that provide genuine personal value to you are never a waste of time. I agree completely. This is probably the best reason to do creative work, whatever the medium: for your own personal enjoyment.
In our American culture, we tend to expect people to specialize in one thing they're good at and then make money from it. This is especially true in the arts. It's okay to play soccer or pick-up basketball if you're not pro material, but because the arts have a product (we paint paintings, write poems, pot vases, sculpt objects, write novels), it is assumed that we will try to sell our products and only be successful if we do so. What's more, we'll only be really successful if we sell a lot of product or make a lot of money.
The reality is, though, that many of us will never write a NY Times bestseller or win an Academy Award for our acting or sell a million copies of the songs we write. We may even be terrific at what we do, but in today's world, success is as much luck as anything, and because we live full lives, we often don't have the time or energy to market ourselves full time and find that lucky coincidence.
But that's no reason not to create. Creating is an essential part of being human. We're designed to sing and dance and draw and put stuff together and play with color and play with words. We're designed to express ourselves. If it brings you joy, if it is of personal value to you, go for it. It is not a waste of time.