So, what's so special about these things? Never eaten or even seen one before in my life. 
They were the first famous bar to have 'excellent macros'. 20+ grams of protein, 15+ grams fiber, <5 grams net carbs, no weird ingredients, usually <200 cals, and they tasted great, all things considered. For a while, no one else offered a bar that even came close to matching these characteristics, to my knowledge.
After a few years, the competition finally caught up, for the most part, in terms of macros. Competing bars still didnt taste quite as good, and didnt have quite as 'good' of a macro profile. Quest still somehow maintained their edge, albeit by a slimmer margin.
Then, quest got sued for false nutrition facts, changed their ingredients as a result, and apparently now they don't taste as good. I've only had one or two of the new bars, so its hard for me to say for sure, but I think they're now roughly on par with everyone else.
For a while, you could only order them online or maybe at supp shops. This is probably why you haven't seen them before. Now, you can find them in many grocery stores and even gas stations.
