To save the SD card mostly. I log to a ring buffer in RAM.
I've had my Raspberry Pis kill dozens of SD cards over the years, so read only can helas for updates, I manually remount read/write when I do maintenance and then remount read/only again when I'm done.
Thanks. I might have a look into doing it for mine, since that seems to make sense. I guess like you said you can just mount the fs rw, and then chroot in to run updates.
No need for chroot, I just say in when I'm on the LAN, remount / and /boot r/w, run the updates and reboot (boots any new kernel and switches back to r/o).
I've had my Raspberry Pis kill dozens of SD cards over the years, so read only can helas for updates, I manually remount read/write when I do maintenance and then remount read/only again when I'm done.