Simple. It's affordable for people who are not making money from their photography, just starting out, or whatever. Not everyone can drop several hundred or a thousand dollars on a lens just because they want one.
This is a reasonable second lens for someone who just has the 18-55mm kit glass. It has image stabilization for a little extra image quality. You'll need that, as the relatively poor aperture will require as much light as you can shove through it.
If you're even an advanced amateur, or a semi-pro, of course this is not the lens for you, but you already knew that. Just because YOU don't want it doesn't mean it doesn't have a market of people who do.
This is a reasonable second lens for someone who just has the 18-55mm kit glass. It has image stabilization for a little extra image quality. You'll need that, as the relatively poor aperture will require as much light as you can shove through it.
If you're even an advanced amateur, or a semi-pro, of course this is not the lens for you, but you already knew that. Just because YOU don't want it doesn't mean it doesn't have a market of people who do.