Every private seller that doesn't list and every buyer that doesn't look may be missing opportunities. It is free, right? Makes no sense to me not to make use of it.
I look to see what's for sale all the time, and if I had something to sell, I'd certainly list it. Some may be geographically challenged (far from many users), or unwilling to drive. But for me, there are surely hundreds of members/visitors within driving distance. Don't understand any wholesale statement that it's not particularly useful or that it isn't why we come here. Don't many initially come here as part of research when looking to buy a tractor? Aren't the used tractors listed in the classifieds a data point that can contribute to their purchase decision? Aren't these buyers also looking for implements? They may just find what they are looking for, in tractor or attachment, right there!
It is a fine line though between a user "service" and an all out free-for-all ad mechanism that is blitzed by dealers. I'm not sure how I feel about dealers using it to advertise. This could make it too ebay-like, loaded with clutter and the same new stuff listed over and over again. Yet, dealers will have some good inventory to offer, and maybe some real deals too. If it were to become this, I'm not sure how it could be governed fairly, efficiently, and with low burden by/to TBN.