Parting out is labor intensive.
First, you have to power wash the entire tractor to get the worst of the crap off.
Then you have to carefully dismantle it, piece by piece. As you do that, you have to inspect each and every part to see whether it's worn out or still usable. The usable parts must be washed clean in a solvent tank, blown dry, tagged and cataloged for the sale.
If you snap off a bolt in the block while removing the exhaust, then what? You either remove that broken bolt or you take a big hit on the hammer price.
You have to pay e-Bay listing fees for each item whether it sells or not and then you pay a selling fee on top. Of course, Paypal also takes a bite when the Buyer sends you payment.
Then comes the fun of finding suitable boxes to ship stuff in, making out address labels, taking items to the post office and paying them. Hopefully you charged enough for shipping because you don't get to come back on the Buyer for your mistakes. In the meantime, you have to deal with the questions that come in about each item, hope that nothing gets lost in the mail and then accept the occasional loss when some scamming buyer says he never got the item, when in fact he did get it.
Can you make money parting out a tractor on e-Bay? Sure but you have to work hard for that money.
Yes Virginia, there are tractors out there that should be parted out because they would cost a lot of time and money to bring them back. Secondly, those tractors are not in short supply nor are they "special" for some reason. Parting out should be done by people who are experts, not by those who don't have a clue what they are doing.
Who would condone parting out a T-90, Torq, Spirit of 76, Golden Demonstrator, Black Knight Demonstrator, any Colt model, Case I80, Case 107, early 108's, Case PK's and a few others.
If someone is just in the biz to find old tractors and part them out for money, then there's no telling what treasures may be destroyed out of sheer ignorance.
