P-38 Canopy
 

Would anyone know why the P-38, despite it's long active service and numerous model upgrades, never had it's canopy changed from it's antiquated hinge system to a bubble top?

Visibility alone would have been greatly enhanced. As well as ease of manufacture.

Re: P-38 Canopy
 

For its time, the P-38 had pretty good rearward visibility - no fuselage behind you. This would have made a bigger difference that getting rid of a few thin frames. A one-piece canopy wouldn't have made as big a difference as it did on conventional aircraft

Blown one-piece canopies back in the day were state of the art for plastic manufacturers. They were quite expensive, and relatively few manufacturers could make them. Maybe the P-51 and P-47 soaked up all the production capacity. When DH began to manufacture the DHC1 in the UK in the early post war period, they went back to a framed canopy because of price and delivery issues of blown canopies at the time.