The resource argument is purely for the fact that parsers are currently downloadable for free, no cost to the players or SE.

Whereas, I believe that there is currently no reskinning program that will allow you to glam, change race, and overlay mounts at your whim...others won't see it but you will...and I don't think there is such a program available for people...

Where it is true that opening parsers to the general populace would make people "transparent" and allow for more accountability, but the chances of people leaving the game because of this...is high.

Tl;dr Parsers are easily available so SE doesn't need to allocate man hours to it. Glam mods are no so easily available.