Although the differences between hot-metal technology and photography seem clear to outsiders, the dominant manufacturers in hot-metal typesetting struggled for years to develop new photo typesetters.
Books and magazines and newspapers needed a whole industry of typesetters, editors, designers, and ultimately publishers who would decide if a book was worthy of that effort.
In fact, initially, they designed their new lines of photo typesetters on the old, hot-metal architecture and tried to incorporate elements of the hot-metal process into the phototypesetting.