These questions highlights the associativity of perception and not necessarily the attributes of products / services that entities are in the business. So, it is easy to infer that brands manifests the perception among the masses. Pepsi is not necessarily a drink for the youth, but perceived to be for the young (remember Youngistaan), as they are the largest customer base for them. Why anyone builds a brand and how to build it?
When a brand is built and seen positively, it becomes very easy, less costly and quite faster to sell products / services for that entity. Even brand can be monitized. Not everyone is able to create a favourable brand and it is definately not in short time. To quote a scenerio, why is it so easy for selectors to choose an IIM candidate over any other, giving benefit of doubt to IIM candidate even if Interview has not gone all that good. It is pre-conceived notion in the mind of Indian recruiters that IIM candidates selected after intense CAT process are bound to be cream-la-cream. Go to France and recruit an IIMer over a non-IIMer and chances are both on the equal footing till the other candidate happens to be from INSEAD, when he will get a edge over IIMer as this institute is French and perceived to be top-rug. Harvard and Stanford are universal brand with positive communication about them that has reached universally. Besides getting real value, it helps to back the brand in at least two other ways - play safe to justify yourself to others and it hides any selection shortcoming one may have!
Changing the human behavior into buying habits and starting to associate best to oneself, is a slow and consistent process with each step involving two things - positive baby step and omni-directional positive communication. To build a brand, it has to be strategically thought, executed in parts and communicated in full (in geography where executed using media and buzz, buzz being more important).