I haven't really had any opportunities to do so since moving into college, but back when I lived at home, I very much enjoyed being able to create my own clothes. It's easy and fun, and overall pretty cost-effective, especially if you want to make something that isn't easy to find online.
For example, I once made my own 1920's Flapper dress for a Gatsby party I went to. Another time, I made a sweatshirt with a "Pride And Prejudice" quote on it that I couldn't find on any fan-based websites.
Furthermore, although materials and sewing machines can get expensive, if you're ambitious, it's easy to save money. You don't have to spend money on buying your own clothes. You won't have to spend money on gas/transit to malls (or shipping, if you prefer online shopping).
Also, all custom-made clothes are custom-fit as well, so there's no need to worry about whether or not that cute top you ordered online will really fit. This works especially well for people who are smaller or larger than average and/or have trouble finding their size!
There's no limit to what you create when you have a sewing machine. If you know how to do it, it's possible! If you have a unique or niche taste, and your style can't exactly be found in retail, try making it yourself!
It's also a lot of fun, and plain HEALTHY to sew! It's a good stress reliever, and it's very rewarding to finish a project. Also, think about how amazing you'll feel when someone compliments your homemade outfit. You'll get to honestly say that you made it yourself, and chances are a lot of people will be impressed by that.
Even if you've never so much touched a sewing machine in your life, you should still try to give it a shot. You may just find your next favorite hobby in the process!