Prior to sueing, someone with a bit of initiative could send an invoice. I suspect many companies, when faced with an actual invoice of some reasonable amount (<$1000) would simply pay it. Some text to the effect of "You didn't contact me before using my text. However, I'm willing to grant a retrospective licence for $.... under the terms at my website [...]".
Will the WMF let me keep half the proceeds? ;-)
It's nothing to do with the WMF, it's not their content. The people that wrote the articles need to send the invoices.