Open v. Closed Cockpits...Why?

[Heeltoe6]

Ok, need a history lesson here. Prototyope/can-am/whatever cars started out open cockipt but then in like the mid 80s, it seems like there was a craze to closed cokpits (probably for better aerodynamic efficiency?). But now everyone has open copckipts again. So my quesiton is why? What caused the change in the first place, and what caused them to change back? What advantages do open cockpits have that they didin't have say 15 yrs ago? The only one I can think of is that it's probably easier and faster for driver changes, and probably cooler in severe heat as well. Course, the flip side is if it rains, the driver must endure the rain. So any info/comments are welcome and appreciated.