It seems that the advertising industry goes in circles. It is always looking for the single "reason." But it is never a single reason. Brand relationships and purchase decisions are both rational and emotional and always impacted by biases. Some of which may be mitigated by greater attention. The goal is always simplicity. It is far easier to be memorable when things are simple. Strong brands are holistically built things that incorporate many attributes, from purpose and CSR to both rational and emotional attributes, and they are incorporated synergistically. The reason for a brand's strength can not be put in a box or be one thing. It is many things, and those things regularly change and evolve with society. This search for the "reason" is people trying to reinvent or rearticulate human nature, things that we know instinctively. So much of building strong brands is common sense. The search for THE reason has gotten old.