Comment 5 for bug 14484

Having the source around means that it is easier to debug problems (you can get
source listings at the crash point, etc).

I guess it would be possible to pull down the source separately, but you'd need
to tell gdb where to find the source code (unless you put the source in the same
place as the package build did). In contrast, with a debuginfo package
everything works out of the box after install (when the user you are trying to
get information from doesn't have much experience, you want to keep the
directions as simple as possible).

Having the paths in the debug info can be useful for software developers too.
Quite often you want full debug information for some of the libraries you use to
help track down bugs in your own code. It means that they don't need to set the
gdb sourcecode search paths each time they want to debug their program.

As far as archives and mirrors go, the Fedora mirrors place the debuginfo
packages in a separate debug/ subdirectory, which makes it easy to perform a
partial mirror that ommits those packages. I guess something similar might work
for a Debian style repository too -- it doesn't matter if the debuginfo packages
aren't mirrored as widely, since they aren't used as much (although when needed,
they are invaluable).