The concept of 'brand purpose' has become ubiquitous in marketing discussions. As a result, there is a risk of the idea falling into disrepute through misunderstanding and misapplication.
So it's probably best to start with a definition of what I mean by 'purpose'.
To my mind, one of the best articulations of what 'purpose' in the world of commerce means is Simon Sinek's rightly admired TED talk, 'How great leaders inspire action', in which he distinguishes between the 'what you do' (product features) from the 'how you do it' (positioning and benefits) and the 'why you do it' (values, belief, purpose).
The reason that the concept of purpose has become so important to marketers is that there have now been a number of high-profile attempts to prove that articulating and delivering a purpose can add to the commercial value of brand or company.
From the 50 high-performing organisations listed in Jim Stengel's book, Grow, which have harnessed brand ideas to surpass their competitors to academic analysis by Joshua Margolis (Harvard), Hillary Elfenbein (Washington) and Jim Walsh (Michigan), there is now a wealth of quantitative data to show that purpose-driven businesses outperform. (Notwithstanding Byron Sharp's acerbic criticism of Stengel's research methodology.)