Does Safely Ejecting From a USB Port Actually Do Anything?

Source; https://www.youtube.com/watch?v=DoZVm2aVBRU
Is there any harm to be incurred by just pulling a flash drive out? Why do we need safe removal at all? Historically, Operating Systems treat disks as objects that can be trusted not to change state suddenly. When reading or writing files, the OS expects the files to remain accessible and not suddenly disappear in mid-read or mid-write.