1) SEO compliant, Marketing. Backlinks can be useful, but I dont use them.
2) Good design, ever pondered the internet and found a site that doesnt look very good and close the window/tab straight away? Well, a good design cuts down the percentage of people doing that.
3) Depending on the subject, add realism to it. For example, I want to make a website to do with 3D development, I would have to add 3D artwork on the main page to gain much more attention, ie: http://gnomonology.com/