Comment 18 for bug 1947601

linux-modules-extra-raspi was added in Impish to attempt to reduce the size of the initrd (and general memory usage) for most users. The update-initramfs tool is configured (by default) to include "most" modules when building the initrd; without linux-modules-extra-raspi installed this results in a ~19MB initrd (again, assuming the default zstd compression). With linux-modules-extra-raspi installed this doubles in size to 38MB, adding several seconds to the boot time and loading a lot of modules that, for most users, are never needed.

Incidentally, a similar split exists in a couple of other places (linux-modules-extra-aws, linux-modules-extra-oracle). If you want to install this package by default on new images, I'd recommend having a look at the "user-data" cloud-init configuration file on the boot partition. This has a few examples in it, including installing extra packages (like linux-modules-extra-raspi) on first boot.