Because they are not on the list of supported processors for W11 published by Microsoft:
https://docs.microsoft.com/en-us/windows-hardware/design/minimum/supported/windows-11-supported-intel-processors
Why are they not on that list? Because Microsoft has decided that your processor does not meet the security requriements of Windows 11.
Whatever the case, your question is for Microsoft.
Doc (not an Intel employee or contractor)
[Windows 11 is the new Vista]
