I grew up in the car business and if we didn't let customers look at the inventory kids or no kids we might as well close the doors.
One of the difference between cars and tractors is that with the cars, kids have to be part of the auto experience.
When we were young, my parents would always check that the back seat was comfortable for the kids when shopping for cars.
With tractors, technically the kids are not using the tractors... although, of course, teenagers often do use the tractors, but not 5 yr olds.
Kids can be destructive, pulling and pushing every lever and button. But, as mentioned, it is a good idea to keep buckets and implements in a "safe position", even if they look pretty with them up. They also function as emergency brakes.
I think too much emphasis is put on keeping kids from falling 2 feet to the ground. I never died from a skinned knee as a kid, even though I had plenty of them.
I've been to a few auto shows. Some people surrounded their cars with "don't touch" signs. If asked politely, I'd always let the kids climb through my car. Although, I must admit that I've had neighbor kids that broke off hard to find "classic parts". Because one kid was holding the door lock from the outside, I caught a kid inside my car grabbing a pair of vice grips to pull up on the door lock button once.
I'm sure tractor dealerships hate repairing damage from particularly destructive kids. But, then, all they need to post is a "you break it, you bought it" sign next to their $100K tractors!!!!
For some people, kids may be part of the buying process, and a dealership will do anything to keep the customers on the lot longer, and looking at more stuff.