Let's step into the waywayback machine.
Before there were all these new-fangled electronic printers there were Teletype machines.
These were electro-mechanical wonders. Lots of springs, levers, contacts, etc..
That is 'adjustable' springs, levers, contacts, etc. Some measurements in 10th's. That's ten thousanths of an inch. Spring length and tension, contact gap and more.
Lubrication was also essential as you might guess. Precise values in precise tech manuals.
Well, the tech goes in to do preventative maintenance on a working machine to make sure all those precise measurements are where they should be.
He gets done and whoops, Teletype is a bit cranky. Customer now very cranky.
I don't remember how long it took before Teletype Corporation issued the edict that virtually all recognize.
If it ain't broke don't fix it, touch it, look at it the wrong way and so forth. Only operate on machines that need life support.
I worked on a ton of these machines, mainly ones that others took apart and then were lost.
It didn't take long to figure out these machines just wore themselves into a working groove regardless of specs.
You could almost call them the first self-adjusting printers.