Its all about marketing, promotion, advertising. What signature campaigns really means is exactly that, promotion of something. How can someone gain from that is easy to explain, more people will hear about them and they will have chance to make nice profit with that.
*Earlier this year, Coca-Cola CEO Muhtar Kent pledged to increase media spending and brand-building initiatives by up to $1 billion by 2016. Coca-Cola spends $565 million on advertising in the U.S., according to Ad Age Datacenter. The company reported spending $3.3 billion on advertising globally in 2013.
*That last one is breathtaking. According to their own Fiscal Reports, Nike spent $3.031 billion on what they call “Demand Creation.” Nike's a little fuzzy on what that means (marketing can be anything from a TV ad buy to a collaboration with a niche shop).
Now you can see how small is this forum, I know we cant compare with this big companies, but this is very good example why companies invest so much in advertising.
I will say that The Rio Games 2016 will be a major marketing event to have these companies who want to promote their brand.
Who is the official soft drink company for them? Is that why you mention Coca-cola in your post as an example? I think they own the soft drink sponsorship of the Olympics for all time.