Rudderrat pretty much nailed it - it's improvement in the window technology. Flight deck windows have to meet pretty demanding bird strike criteria - 35 years ago about the only way to do that with large windows was to make them flat plates. The flight deck structure and windows (what Boeing calls "Section 41) is very expensive to design and certify - as a result the 757, 767, and 777 all use the same Section 41. The design was pretty much optimized for the 767, then adapted to the 757 (that's why there is a step down onto the 757 flight deck). When the 777 came along 15 years later it was again adapted to the larger fuselage (the nose of the 777 has always had a bit of a funny profile as a result).
I wouldn't be surprised if the Airbus equivalent uses pretty much the same structure on the A330 as is used on the A300, A310, and A340 - so once again 1970's design.
For the 787, advances in technology allow big, curved, strong, windows that permitted the nose shape to be better optimized.
BTW, a little trivia - during the bird strike testing of the 767 flight deck windows, one of the birds wasn't properly aimed and 'missed high' - and went right through the aluminum skin
. Given there are some pretty important electronics it that area, a doubler plate was quickly implemented into production aircraft
