Moto Miwa comments

There are many reasons for this, but traditionally it is more based on reporting/summarizing of events and ideas within the firm. The micro-departmental operations are not so transparent sometimes with things taking place outside of the office often, such as deals signed by handshakes, and agreements made over a dinner or cocktail lounge, which have much more gravity than in Western companies that usually do things more formally with documents and signatures during business hours.

So with a lot of departments, subsidiaries, or managerial freedom they might have in a fast paced company, one of the ways to keep in organization is these summary, reporting, and greeting meetings. Today it is held over teleconference much more, but older customs dictate that a lot of the meetings must still take place in presence of the senior members in charge, and be blessed by them to charge through each phase of projects.