In order to make these attributes visible, you need to perform following steps:
1. Edit c:\windows\system32\dssec.dat file in notepad.
2. Search for [user]
3. Underneath [user], look for ServicePrincipalName=7
4. Change the value from 7 to 0.
5. Save the file and reopen Active Directory Users and Computers console.
You will now be able to see Read ServicePrincipalName and Write ServicePrincipalName for User Objects to delegate control.