Why do we need this in a kernel? Why not just serialize the essentials of the apps states and re-load it after reboot/sign-in? I'd prefer the desktop environme

Why do we need this in a kernel? Why not just serialize the essentials of the apps states and re-load it after reboot/sign-in? I'd prefer the desktop environment to remember which apps were running including which documents were opened in them and their windows positions and just re-launch everything at start-up. Given how fast does everything cold-boot today thanks to modern SSDs, I wouldn't even use standby/hibernate if this worked this way.