This would give the ability to place dynamic code in the URL field for parsing when the page is loaded.
An example use case is when using CouchCMS, the system gives the ability to insert the site's base URL by using
<cms:show k_site_link />
The current behaviour is that Webflow will turn the above into:
http://<cms:show k_site_link />
Adding an automatic "http://" at the start, and url encoding the custom html tag that CouchCMS would parse before displaying the page.
Having to go around your pages to convert all of these links manually every time you update the site is painful.
This could also be useful if you wanted to use custom php functions in your URL's to be parsed at execution time. A lot of sites that are exported are turned into PHP pages.