I'll confess my ignorance here. It's been many many years since I've been around a "farm" size tractor. Do the "newer" ones have seat safety switches?
All the new ones do (last 15-20 years) but they serve a different purpose mostly. Not going to fall off a tractor in an enclosed cab.
They will mostly warn you of things that may still be turned on when you leave the seat. For example they will flash a warning light and a short buzzer if you leave the seat while the pto is still running. It just reminds you to shut it off before you leave the tractor but it is not mandatory to do so, for good reason. Things like grain augers, irrigation pumps, feed grinders, etc have to keep running with no operator present.
It will also give a warning if a hydraulic circuit is still engaged. And it will prevent the tractor from starting on some of them so a person can not be off the tractor to jump start across the solenoid or something like that.
Probably some other things they do that I do not recall. They are not really objectionable and serve a useful purpose.
But it is assumed professionals are running the machine so they are not quite as cumbersome as some of the hobby and consumer market stuff.
