Yes & then there are brand new & nearly new tractors that engine won't start/run or transmission won't operate as designed because of a part failure or regen failure.6,500 hrs, 6,800 hrs, 8,000 hrs, 10,500 hrs, are still lots of times that everything in any engine is going round, and round!
The continued hard pulling by farm tractors may affect engine wear, but in either type machine with the same total hours, the same parts are all moving/wearing constantly.
Utility tractors usually have many more cold starts, and that can certainly be an engine wear issue.