It's because you look at it as not a world, which it really is. It's like people that go out and do things alone in real life, there's no real difference. Some people enjoy this type of game, but they don't enjoy being forced into groups to do everything. Many of them also don't enjoy being looked down upon by people who refuse to understand their viewpoint because they refuse to look at something for what it is and not what they want it to be.
One of the issues you're ignoring or not even looking at is that not everyone has a posse of friends who will help them at a drop of a hat. DF is intended for those very situations. You got home from work early, and want to jump on and get something done. But, oh, none of your friends are on, and it might take a while to get a server group put together, in which time DF could very well have you in a group and on your way.
Also as Horo said, grouping with friends is indeed likely to be faster and more efficient than solo queuing for the roulette. The problem is, people see the reward and automatically think they're being punished or think they should get the reward too, but without fulfilling the conditions. It's an opportunity cost. Play with your group of friends and get dungeons done faster, which also has no limit per day. Or you can solo queue with the roulette and get a bonus reward, but the runs are likely to go slower as well since you will likely get newer players.
Again, key term here is "Opportunity Cost". You're not being punished, to think so is to play the victim when you aren't.
