It's because of MMORPGs. I was pretty adamant about not treating Destiny like a MMORPG (like I made some comments in the "only one area per planet" thread) until Mr. Scarab Lord came out with this interview showing me that Bungie actually considers Destiny a MMORPG.
Raids always get the most exciting and interesting mechanics. Everything else kind of exists just to prepare you for the raids. A large part of development time goes towards the raids. It's comparing the daily grinding and 5 person dungeons in WoW to Siege of Orgrimmar. It's totally different and SoO is infinitely more exciting and interesting as a grind than the other PVE offerings at 90.
Based on Mr. Scarab Lord's history and the interview and looking at other games with raids, I would have to believe that Destiny falls in line with MMORPG raid-based content design.
Which is why I said my last paragraph in the post you quoted. I think Bungie really needs to come out to show what else they have on offer other than vendor currency grinds.
His name is Luke Smith. You can drop the name calling now.