How much of the total volume of the device was the case/housing?
I suppose the glue-everything approach is partly due to the desire of making a device very thin. There's no room for strong, load-bearing outer case, the internals are load-bearing.
I suspect manufacturing has something to do with gluing too. Afaik screws are expensive compared with glue, and their assembly involves slow humans or expensive robots.
It's been a long time, but the gasket itself was probably a millimetre or two thick, squeezed extremely tightly by the screws in the battery cover. It ran on AA or AAA batteries, and they took about about half or a third of the depth.
I suppose the glue-everything approach is partly due to the desire of making a device very thin. There's no room for strong, load-bearing outer case, the internals are load-bearing.