Why is the whenCreated property not fetched when querying AD from PowerShell?

Question

PowerShell

I give

Get-ADUser -Filter *  -Properties whenCreated | Select Name, whenCreated

at the output, most of the records with an empty whenCreated field, but for some, it is still filled.
If I look through ADSIEdit, then for those accounts for which the script displayed an empty value, it is not empty.