why does an in-tree loadable module taint the kernel

serio_raw is apparently tainting the kernel when its modprobed. why ? other modules load properly, no code changes to this module bash-5.1# dmesg | grep -i taint [ 6.517150] serio_raw: module verification failed: signature and/or required key missing - tainting kernel [ 7.449072] CPU: 0 PID: 203 Comm: systemd-udevd Tainted: G E 5.13.0-rc6-lm1-00004-g28dc6f490a7f #106