I planted sunflowers the first year that I started my garden at this house and I have never had to plant them since. The birds do a wonderful job of spreading the seeds all over my garden. In the spring I just move them where I really want them to grow. Most of my sunflowers are plain yellow variety (most likely from the black oil seed that I feed the birds. But there are also plenty from that original variety which was a multi-tone flower.
Sunflowers have always been one of my favorite flowers. I use sunflowers in my garden to create a screen to block out the view of the street and the alley, as well as giving our gazebo a bit of privacy. They also provide a little shade for some of my plants that do not prefer full, all-day sun. And they are fantastic natural bird feeders. I usually leave the plants in place all winter so that the chickadees and nuthatches can pick at them. I have never tried to collect the seeds for myself since the birds will eat them while they are still green and usually have the flower heads all picked apart by time the seeds ripen enough for me.
I don't see a lot of gardeners grow sunflowers. I'm not sure if it is because they don't like them or they think they are too tall for their gardens. Maybe they think that they have to have full sun. I have sunflowers of all heights and I even have a few growing in mostly shade! I didn't plant them in the shade, they just started growing there. I am going to try to collect the seeds from these to get a shade tolerant variety that maybe other people could grow in their garden.