The world loves a baby. Also the birth can ensure the continuation of an institution like a company - or the House of Windsor. British royalty is threatened in these times of austerity. Without a sense of newness and continuity the institution could be tossed as an expensive anachronism which isn't worth the tourist dollars. After all, travel agencies can promote visits to where "Downton Abbey" is being set and directed.
So, it's a lucky break for the House of Windsor that Kate Middleton has a bun in the oven. That ensures the royals are safe for at least one more generation.