Open concept offices - why ?

My hypothesis: Once upon a time, most bosses stayed in their own offices in their own world, with their doors usually closed and one needed to make an appointment to get an audience. Then one day, one enlightened one decided to have an open door policy so that staff could approach them more easily. The next enlightened one decided that to promote even more interaction, there should be no offices, everyone should just sit with everyone - in the name of better collaboration & communication. This seemed to make lots of sense for certain industries like the creative ones who need to discuss a lot , and for the traders. Then someone decided that there should be no partitions, let everything be open concept. The idea caught on. And before we knew it, everyone else just copied blindly, regardless of the nature of their work. 

Well, this is a good concept theoretically, until you have hardworking, high volumed colleagues who am not aware of their own volumes, until you need to focus on writing or computing numbers in peace, until you cannot hear the other person on the line due to the noise pollution, until you can't find an available meeting room to escape to, until the productivity actually drops rather than increase.

Hence, perhaps the only survival method is to get noise cancellation headphones to preserve one's sanity. However,  one must also be careful not to get the kind that blocks out airplane engines sounds but not flight announcements  (as that might totally defeat the point). Just can't help but wonder who's the right party to pay for the bill - the company, the pollutant or the polluted?