Point well taken, but what if you are the third owner of a tractor and decide to sell it. How do you know what labels might have been there to begin with?
There must be some limit to this worry...somewhere...
The first thing I do with anything I buy is get every shop manual, parts manual, and operating manual for it that I can find. I'm a tinkerer, engineer, and more curious than a cat. I like to know how things work. That's how I generally find out what labels belong where, and probably whether or not they can still be had. I can't fix everything, and I accept that. But I'm old school, and like another said, if I don't feel like I can do something safely, I'm hiring someone with better equipment and more know-how. If I can't get the label, I'll either make my own or do something to draw attention to or guard a pinch point or dangerous (but necessary) part. I've had 40 years engineering experience in heavy industry (any kind you can think of and some you probably can't imagine), and yes, I'm probably a little more overboard with safety than some. I also grew up in the 60's and 70's, out on a farm, so I probably have a lot more walking around sense than some of the engineers I have worked with, too. There is a balance, but it is definitely smarter to err on the side of caution. It keeps lawyers out of the picture.
Is there an end to this? Well, yeah, probably, when lawyers have all the money and there's no more to get, and no one manufactures anything any more. Hang on, did I just figure out why so much industry is leaving this country? Sadly, some intelligence to operate a product and maintain control of it is no longer a requirement for ownership or operation. And it's ALWAYS the machine's fault when something goes wrong for anyone born after 1990. They could NEVER be at fault. The more preferable end would be that stupid people deepen the gene pool by doing themselves in, and taking a few lawyers with them. "Hey y'all, holmubeer and watchiss!" There's your sign. Ya just can't fix stupid. Where you draw the line is completely up to you. You and I probably don't have the same threshold for risk tolerance.
Remember, people in born in the last 30 years eat laundry detergent for a challenge. I can't say I've EVER wanted soap in my mouth, especially when I was a kid and that was the consequence of using four-letter-words that are not in a grammar school dictionary. I'm just glad the children's home I spent my childhood in didn't buy Palmolive. Oh fudge!