They've had 70 years to change their mind. They haven't. They like things simple. I'm surprised they'll sell you cheese. See also > Why does In-N-Out not serve bacon? read more
It would require In-N-Out to put out a burger that wouldn't taste like an In-N-Out burger. It would taste at best like good bacon (assuming that they would cook high-quality bacon to order, which would throw off the workflow per Ryan's answer) and at worst would taste like any other fast-food bacon burger. read more
Apparently, a few In-N-Out locations are responding to the cat-calls of #PiggyStyle in their restaurants by adding bacon to their famously simple burgers. read more
On Jan 3., In-N-Out expanded its menu — which largely consists of burgers, fries and milkshakes — to include hot cocoa made with Ghirardelli chocolate. But while some people on social media went “cocoa” for the drink, others were left wondering why the restaurant still doesn't offer bacon, or any kind of breakfast sandwich. read more