Well it's about about the stock market and announcing revenue within a certain quarter. All of those pre-orders matter to increase revenue and these companies don't want to let it slip away by delaying a product.
To be brutally honest, we are the ones to blame to a large extent. If we didn't rush to order games unseen and kept buying bad games (CoD for example has been wonky since black ops) companies would be in much more of a rush to fix the problems.
Although a crap load of us complain about how bad Advance Warfare is, everytime I log onto the PS4 half of my friends list is playing that game. So a lot of people are buying and playing a "broken" game although the bitch about it a lot.
CoD equaled Destiny's sales of the first day. If I'm the CEO or the CFO I'm not seeing much of a problem.
If there was not revenue however, they would feel pressure to fix the problem.