It's actually really important. Google doesn't have issues with it at all, it only improves SEO because of the way google indexes individual pages. If you have keywords in your URL, thats a huge positive. So thats another reason why they should be re-written.
If google finds duplicate content on several pages, it will only index one of the pages, which is why I tell everyone that having unique content for each page is important for SEO. Plus if google finds the same content on another page, it will make the page invisible to the search engine's result pages.
Query string pages also make the url longer so that the keyword when for google becomes insignificant. For example, if you have a page.
index.html or index.htm it's a lot different than index.php?id=24 where there is no unique keyword. Doing it the first way adds an extra keyword to virtually every page
make a rule code for a url rewrite and get rid of all of them. Because the truth is as you've asked, the first option is more SEO friendly.