I think Huxley has written Chapter the three the way he has for a number of different reasons. Number one: he wants to educate us about Brave New World's past (such as the Nine Years war) and its present views about things (Mustapha Mond describes motherhood and families etc and the students are horrified - this highlights their reversed morals) and some of the details about how the conditioning and decanting centre works (hypnopaedia etc) without boring us too much. Number two: he wants to introduce several characters at once and by doing this he juxtaposes their differences in values and personality. Thirdly I think Huxley is using this chapter as a powerful metaphor for the "Brave New World". He is showing that even in this world of stability there is chaos and a loss of identity (this is shown as it is very hard for us to identify who is speaking). It is a very clever and purposeful piece of writitng.
Huxley's use of dialog allows the reader to learn a lot of 'back story' on this new world and the way people interact with one another. Without having to 'tell' what that world is like, he 'shows' how it is by the way the people react to various discussions (mothers for example). The main idea is that there has been a terrible cost for 'stability' and 'order' in this world. Individuality and creativity have been lost....and in the end a good deal of humanity.