The answer to your unspoken question is: what difference does it make if I want to solo in an MMORPG? If I and enough other people want to do it, it's a game model that can succeed. Telling me I should go play a non-online game is beside the point, and the point is "sell people what they want, whether it makes any sense to you or not". It doesn't have to make sense that lots of people want to solo in an MMO environment, it only has to be a profitable model.
Instead of solo content being the red-headed stepchild of MMO content, providing rewards that gouping and raiding enthusiasts will tolerate in their game without rage-quitting, why doesn't some enterprising development team turn the tables? Make solo content superior (or at least equal) to group and raiding content. After all, it's not like it takes a lot of skill to sit there in a 40-man raid and do what someone else tells you to do for a couple of hours. It's not like it takes more skill in a group where other, better players can make up for your deficiencies.
Here's the question that invariably comes up in this argument: given that you can gain equal or better rewards via solo play, what motivation will there be to group? Note the assumption hidden in the question: that solo content will necessarily be easier than group or raid content. AS IF there aren't as many or more players that would be utterly incapable of getting their character trough properly tuned, difficult solo content, and would require group and raid managers to help get them through comparable group or raid content. How many people are carried through group or raid content by others who are just better players and/or managers, or just know stuff about the content that others have no clue about?
In solo content you're on your own, and success or failure is all yours. Nobody to bail you out, nobody to tell you what to do, and falling asleep at the helm won't go unnoticed as you are still awarded your items if it is your turn to get them. For the few that organize and direct such raids, it is an achievement; for the other 35 or so people, it's just doing what you're told passably well. Big deal.
Now, I'm not saying ALL MMOG's should offer superior (or at least equal) rewards for solo content, but I am saying that this group and raid-centric model doesn't need to persist in every stinking MMOG that comes out. The idea that group content is "harder" and should offer better rewards is a self-fulfilling prophecy based on a myth. It's my contention that a large percentage of raids and groups are populated by players that couldn't handle well-tuned, difficult content on their own, and require better players, more informed players and managers to overcome their deficiencies and get them through such content.
I mean, what makes more sense - admiring gear and achievements worn or displayed by those that perhaps fell asleep during a 40-man raid, or were gained perhaps by 4 other players making up for his or her poor skill and ignorance of content mechanics, or worn by someone who you know had to get through certain content by themselves, with all necessary knowledge and skill?