Why keep personal files and apps option greyed out during windows 11 upgrade?

Performing an in-place upgrade to Windows 11 using the Installation Assistant generally preserves your files and apps, but if the Keep personal files and apps greyed out, and you proceed without it, there are some potential disadvantages.

Without properly selecting the option to keep files and apps, there's a chance that some data or applications may be lost or become corrupted during the upgrade process. Some existing apps may not function correctly after the upgrade if they are incompatible with Windows 11 or if they are not preserved properly. Upgrading without a clean install may carry over existing system issues, clutter, or malware, which could affect performance or stability.

If the upgrade doesn't proceed smoothly and Keep files and apps greyed out, you might have more difficulty troubleshooting problems since a clean install (which wipes everything) is often simpler to diagnose.  If problems occur, rolling back to Windows 10 may be more complicated or less reliable when upgrading in-place with preserved files, especially if the upgrade process encounters issues. Attempting to keep apps and files during an upgrade that isn't properly configured might result in errors, requiring additional troubleshooting or reinstallation of some applications.