Why Is the object class "top" specified in a ldif entry?

Question

Every ldif entry requires the top object class to be specified. Here is an example:

dn: uid=steves,ou=users,ou=SWG, dc=com
uid: steves
userPassword:: hello123
objectClass: inetOrgPerson
objectClass: top
objectClass: person
objectClass: organizationalPerson
sn: Wiley
cn: Steves

If every type, such as inetOrgPerson, is a subclass of the object class "top", why does the object class have to be specified.

I have looked at the RFC and it does not say why it needs to be there other than it needs to be there.