This is educated speculation on my part, as was mentioned before Sony chose not to have dlna on the PS4. Its not anything special to have it implemented. If they can have vita remote play baked in they could have had dlna working also. Sony wants to push their own cable iptv and movie & music store. So from a business standpoint why would they allow dlna or its successor on its platform if it will have to compete with the cable companies on its own box?
This is Sony most important product right now, They want to make money and not lose the billions they did on PS3. Sony was fully prepared to have the PS4 locked down tighter than the Xbox One but they was smart enough to back down at the last minute when they saw the backlash from MS. These policies you see now are just remnants of their abandoned policy.