Why are page titles on some websites clickable URLs?

It allows you to right-click on it and choose Copy link location (or equivalent) so that you can easily paste it in an email for example. This requires less time than copying it from the location bar, and some people run their browser without a visible location bar to save previous screen space.

More than anything, it provides a link to the default state of the page.

For example, for this very stack overflow page it is a user can get here through any of the following non-default links:

• Why are Page Titles on some websites (including Stack Overflow) Clickable URLs?
• https://stackoverflow.com/questions/904381#foobar
• https://stackoverflow.com/questions/904381?sort=date

While the default link is actually:

• Why are Page Titles on some websites (including Stack Overflow) Clickable URLs?

If users are unable to get to the default state, they end up bookmarking or emailing the non-default link which propagates to new users and the problem just multiplies.

Clicking on the title link of the post will restore the default state and strip off any query parameters (?sort=date), named anchors (#foobar) and fix the story slug (/why-are-page-titles/...).