If you are a musician and wanted a car, would you need to learn design, mechanical engineering, welding, electronics, glass making, etc, or would you just go to an automobile dealer?
No, but you're mistaking a couple things. If you want a car, you're expected to know how to drive as well as how to fill the gas tank and change the oil (or who to call when you don't know how), right?
By deciding to run self-hosted WordPress, you're expected to know how to run a website (this is driving, in the above metaphor). You can use pre-fab themes if you don't know how to do that, but you're at the behest of someone else (this is changing the oil). Filling the gas tank is writing a post. :)
If it all just seems much to much, I would suggest instead running a wordpress.com blog, and if you really like it after a while, consider either learning what you'll need to host a website, or utilizing some of the premium WP features.