Loading form values from database when editing versus set_value() for validation

[eluser]Thorpe Obazee[/eluser]
I can't understand. Why can't you use set_value()?

Code:

<input type="text" class="text" name="post_title" id="post_title" value="<?php echo set_value('post_title', $page->post_title);?>">

In this code, the $page->post_title is the data from the db. When I update, it still loads the data from the db which might be different already.