The term bean to bar chocolate started as a way for small chocolate makers to distinguish their chocolate from both chocolatiers, and also mass produced chocolate. Starting around 2005, craft chocolate makers began operating in the small batch territory, some producing just a few hundred bars a month. After buying small quantities of cacao, they were cleaning, roasting, cracking, winnowing, and grinding the cacao beans themselves. They began calling this process "bean to bar," meaning from cacao bean to chocolate bar, as shorthand for the long process of micro-batch chocolate making, whereas chocolatiers melt pre-made chocolate to make chocolate confections.
These early bean to bar chocolate makers often started out because they wanted to learn how chocolate is made, and continued after realizing how much control small batch chocolate makers have over the final product. Bean to bar chocolate makers control where they source each ingredient, often making single origin chocolates to show off the complexity of each cacao. The movement of bean to bar chocolate has continued to gain momentum because consumers can also taste this difference. While industrial chocolate tastes flat and lacks provenance, bean to bar chocolate contains a multitude of flavors and stories.
To achieve these results, makers have to purchase small amounts of ingredients at a time, and bootstrap most of their equipment. This makes bean to bar chocolate more expensive than industrial chocolate, so small makers have had to educate their customers as to why their chocolate tastes so different and costs so much more than other “premium” chocolates. Eventually, the term "bean to bar" became global shorthand for "small batch chocolate." Starting around 2015, larger chocolate companies started noticing the popularity of bean to bar chocolate and began co-opting the term.
While the implication of and culture surrounding bean to bar is strong, there's no legal definition for the term. It's actually just a literal description of the product. If you make chocolate directly from cacao beans rather than prepared cacao mass, you've made bean to bar chocolate. If your company owns the processing facility where the cacao mass was produced, you might stretch your definition to fit that.
But thousand-pound batches of chocolate go against the small-batch feel & origins of the bean to bar chocolate movement. So while the term was necessary for the market at the time, which had almost no knowledge of how chocolate was even made, many makers have begun using the term "craft chocolate". Now that the premium chocolate industry has built a base in many parts of the world, it's drawing comparisons to craft beer and craft coffee, connecting delicious flavors with the ideals of handiwork and traceability.