A better question is "Why will stern be online?"
IT'll hardly ever work, ops will never use it, location Wi-Fi tends to be too flaky and change passwords often...
The effort it would take for a Stern pinball machine to operate on Wi-Fi efficiently and correctly would negate any supposed convinience to an op as far as software and firmware updates. They'd be "servicing" the game far more often than they do now just to keep the Wi-Fi connection hunky dory.
Not to mention most ops are in a cash-heavy business and also crazy (and paranoid) and aren't likely going to be interested in even the slightest possibility of their audits and adjustments being hacked.
Just like a million other things that people think Stern can just whip up in 5 seconds to give a whirl, it would divert time, money, and resources to something that simply isn't very useful.