Bing is to retire one of it's really useful tools from Webmaster Tools, Link Explorer, on October 1, 2015.
Bing says that it's index has grown significantly since Link Explorer was introduced, and that it means it will no longer run the reports.
It seems to me that, perhaps, Link Explorer was taking too great a resource, and that it wasn't generating anything of value for Bing and Microsoft; only for people using it.
Saying goodbye is never easy, but the time has come to do just that with a member of the Bing Webmaster Tools family: starting October 1st, 2015 we are shutting down Link Explorer. Bing To Close Link Explorer October 1, 2015 [blogs.bing.com]
Although this is gone, the the Inbound Links tool is still available.