A lot of people don't care to understand the history of their games. It's critical when you service a game. As others have stated, once I get a game up and running properly, I play it 50ish times until I am satisfied that every single thing not only works, but will continue to work. Then it is show, league, or for sale worthy.

There is always something just waiting to overheat or break when you start using a game that has been sitting for months or even decades. Those things do not always appear in the first few plays. You don't know the environment it was stored, how it was abused, what else the owner did to it, or what quick fixes the operator used to just force it to keep taking quarters.