Lots of organizations nowadays do NOT provide emails but only contacts, social media or online feedback / query forms. There are usually practical reasons behind these business decisions. While HHonors corporate may have a policy of not passing out email address of individual properties, they do still pass along the message itself and the property will then normally reach out to you directly. This could in fact be a convenience as you can just reach out to any Hilton properties just through 1 contact point.