Why do some Wiki pages not show the "Edit" link?

Why do some Wiki pages not show the "Edit" link?

Meaning I can't edit the content......

Is there a reason for this?

There are Wikipedia pages that have been locked (protected or semi-protected) so that only administrators and confirmed account can edit them. This is to prevent vandalism or defamation on a Wikipedia page. You can read more about this on their Protection Policy page.

http://en.wikipedia.org/wiki/Wikipedia:Protection_policy