Zotero will only print a URL if there is no page range - i.e. if the journal article is presumably online only. That's the recommended practice for all CSL implementations. The CSL editor as well as Zotero's test panel currently don't reflect that behavior, unfortunately. So this would be quite rare in any case- I'd be curious how pre-print publications are cited? More typically that'd be via DOI, and we could test for that, reducing the likelihood of getting a URL in the bibliography (which I agree is very rare if it ever occurs) even further. I'm thinking of things like government reports posted online. An option would be to take the "internet" note here out and restrict the access macro to type=webpage only. I'm just hesitant to take any way to cite online sources out completely.

(Pubmed URLs should not be in the URL field anyway (they should never be cited), the the Zotero translator behavior was changed a couple of months ago, not sure what other programs do.)