It is strange that System Restore is disabled by default in Windows 11, however, it is known that large Windows 11 updates will delete all restore points to avoid system corruption that may be caused by a system restore after an update, causing old and new system files to become mixed in the operating system.
Microsoft are currently working on a new function named Point-in-time Restore for Windows 11, it is being tested on the Insider builds at the moment, and while the old System Restore would only restore Windows System files and the registry, the new function will revert the PC back to its exact state at a point in time and is reported as a very effective recovery option, should Windows fail to boot up.