What I've read re old emulsions are films designed about or before WW2.
ORWO, that later become other company (Adox?) was the fist one to manufacture a thin emulsion - by the 60's, if I recall correctly. The other manufacturers followed it.

The reason is not economics - it's related to boosting sharpness (as light travel the depht of film, it difuses and smear).

Jorge O