It depends on whether you're looking for a new or a used truck.
I just spent several months perusing the used 13-16 Explorers in my area (St Louis) before finally finding a great price on a '15 XLT with the factory towing package. My observation was that the great majority of the used vehicles I found were lease, rental, or other "program" cars and those never had the towing package. The one I finally found was originally factory ordered and sold by a rural dealer and was traded back in to the same dealer where I found it about 80 miles away.
Unfortunately, the greatest majority of reselling suburban dealers didn't bother to note the inclusion of the towing package even when it was present. I had to look up the "original window sticker" on those Ford dealers that provided the link or look up the VIN on ETIS to see how it was built. I probably looked at several hundred stickers or ETIS build reports over the course of that search. On a lot of the dealer listings, if they showed a rear view of the bumper, a good number of candidates can be quickly eliminated. However, somewhere along the line, the profile of the bumper cover was changed so it wasn't quite as obvious just by looking at the photos and deeper digging was needed.
As for the Sport and the towing package, it became standard on the 2015 model and was an option before that. IIRC, the Platinum included it from 11-on.