let's go through the facts.
Both have the same phone.
same firmware (meaning you both have 4.3)
you are both STOCK and NOT ROOTED
a factory reset does not bring back this option.
something is missing, because the option should be there if the phone is NOT ROOTED and is stock.
if this is the case, and a facotry reset did nto bring it back, the phone is defective and needs to be sent in to HTC for repairs, OR if your husband wants to ROOT the phone, he may be able to do this and can perhaps gain even more options over stock.
there is no setting to hide this option, so there is not anything you can do other than to
verify the factory reset worked
the phone is not rooted
riddle me this batman, did the phone EVER HAVE the option? what happened to make the option go away?