Yes, that would happen if you installed the particular header package (linux-headers-2.6.32-19-generic) before installing dkms or nvidia-current. Because linux-headers is a virtual package provided by linux-headers-2.6.32-19-generic, the dependency is considered satisfied and you will not automatically get linux-headers-generic.
We cannot add a linux-headers-generic dependency to dkms because there are different metapackages for the other kernels (linux-header-server, linux-headers-rt, and so on) as well as custom kernels.
Yes, that would happen if you installed the particular header package (linux- headers- 2.6.32- 19-generic) before installing dkms or nvidia-current. Because linux-headers is a virtual package provided by linux-headers- 2.6.32- 19-generic, the dependency is considered satisfied and you will not automatically get linux-headers- generic.
We cannot add a linux-headers- generic dependency to dkms because there are different metapackages for the other kernels (linux- header- server, linux-headers-rt, and so on) as well as custom kernels.