Why do teams hold off on blockbuster deals until the last minute? I get that they hope to drive the price up, but isn't it as likely that the price would go down if other suitors fall away? The Rockets pulled off their big Ralph Sampson trade in December of 1988 (?) as I recall. Was THAT at the trade deadline in that era? No one does it so there must be some powerful reason for all this procrastination but if I'm trying to improve my team for a playoff push, it seems like doing a deal in January or February and having them together for an extra 4-6 weeks could be a big benefit.
A lot of the deals are made as a last resort. They want to make it work until all hope is lost. Before the deadline asking prices are too high but you can get bargains or reasonable prices for blue chip players at the deadline. Someone like Morey isn't going to make trades just for the sake of doing them, it has to make sense for both sides too.