Short answer: because you appreciate the site and feel like doing so.

Long answer: I run ads on the site in order to offset the costs of producing and running it, and these ads are sufficient to keep things running. Trust me, you’d know if they weren’t ;)

The reality is that most people who feel like donating are just donating because they genuinely appreciate the site and *asked* to donate. You are under no obligation to monitarily contribute to the site. If you want to help out there are lots of ways to without opening your wallet:

• Write something for the wiki, or fix something.
• Help out people in the forums.
• Got photoshop skills? Help the sig team.

If you do feel like donating, there’s the button, if not, no worries!