#caddies
Going back through some early CD-ROM source articles (1988 and before) it
seems caddies allowed the design of drives that would fit in a standard
half-height computer bay.
From the CD-DATA REPORT (1987): "… The reasons for requiring the use of
cartridges vary from drive to drive. In the case of half-height drives, the
limited height of the drive precludes the use of a mechanism to elevate the
disc on a spindle prior to spinning and reading. Instead the disc must be
used in the same plane in which it is inserted. The cartridge makes such
"spinning in place" possible."
The idea that caddies exist primarily to protect discs came along later,
primarily from people who didn't know the technical necessity of them.
Now, as to your question, "Why can't the publishers just slap the caddy
on?" Very simple. I have two drives, neither require caddies — SO THERE!
Just jokin' of course.
Actually when caddies first came out they weren't standardized. A CD-ROM
producer had no way of knowing what type of caddy you needed — or if you
didn't need any at all. There are still some non-standard caddies out there
— and of course there are all those machines that don't need them. I think
you'll see more and more non-caddy machines as drive technology improves.
Cheers!