Duh. I just found a wonderful gaming analog to the question in the OP...
Why are people bothered by the idea of no free will?
Why are some gamers bothered by a lack of character death in a game, or railroading plots?
The basic answer is probably the same - it is a question of whether you get to make "meaningful choices".
good point. the concept of choice vs. Choice (capital C implying meaningful choice).
A GM could supply a player with a dungeon crossroads and imply he has a choice. But without any information, it doesn't really matter which corridor he takes. It's not a meaningful choice.
Furthermore, the GM could stick orcs down at the end of whatever hallway he chooses, further un-differentiating the choices.
Conversely, in real life, people will assign blame and responsibility by saying the person had a choice. For example, saying poor people are poor because they made bad choices and didn't find a job.
But that's a half-accurate assessment. Obviously, a guy who lost his job and is in the bread line must have made some choice in the past that led him to his current state. Maybe he should have been more diplomatic in that one staff meeting that rubbed his Director wrong and caused him to get a lower score on his annual review, which put him in the queue for next to be laid off.
However, this poor guy didn't have that knowledge when he made that choice, didn't even know it was a factor in his future fate (much like that choice of generic dungeon corridors).
His personality wiring makes him less diplomatic and more direct, so he's naturally predisposed to saying something career limiting. it's a predictable outcome.
to further judge him and his failure to get a job, one has to consider that his fate lies in other people's choices as well. Somebody else makes the decision to pass on him and go with the cheaper unexperienced kid.
What usually bugs me the most on the topic of choice (which does bind back to lack of free will) is that when something bad happens, folks will point and say "you chose to do that" as if the person could have chosen differently. Yet, when you look at the situation, and the psychological make-up of the person, it's a foregone conclusion on the path that person would take with the information the person had at hand.
To my eye, I can guess or predict how someone will likely behave. After the fact, I can review a situation and see how somebody comes to be where they are at. At that point, while I see the choice points they made that they had an opportunity to do something different, the path they actually chose is laid in as a railroad.
The GM could argue, "you guys COULD have chosen to betray the king and side with the demon", but to me, I look at the players, and I know that certain "choices" are not an option for them. They don't really have free will to burn the village, eat the orphans and partner up with the demon, because that's just not a path they will choose. (note, there are plenty of players who WILL do just that). It's a case of knowing your players. In my case, when I know my players, I know how they will respond to stimuli and can predict their response with reasonable reliability.
Thus, I can manipulate them into doing the adeventure, rescuing the princess, etc. They don't really have a choice, because I already know how they will choose because I frame the choice in a way that sets up the response I can rely on. If I don't think my players are likely to rescue a princess, I don't set that kind of situation up.
So, because I see people as predictable and manipulatable to some extent (not saying I am actually good at those things), I tend to see that as a lack of free will on their part.