Why is Drupal urlencoding in tpl output?
Drupal is not URL encoding in the template output, it doesn't try to make that sort of blind string replace anywhere.

If the URL was prepared using any of Drupal's url() function, which is likely if you're using well written modules, then you should expect the query parameters to be properly encoded.

Drupal tries hard to conform to standards, you're probably going to find it more trouble than it's worth to get it to produce an invalid URL (which your desired result would be); it would be easier to simply write your own invalid version of url() and use that to prepare the content.