Noise traders ultimately create an even greater incentive for accurate prediction. The fact that the odds are set at the start and never change just proves that there's very little change in relevant information about upcoming sport games, races etc. where regulated bets happen. That's totally normal. Bets about real-world events are a rather different matter though.

No, they don't. If you have a line that is beatable, that line has been open for a long time, and you have informed people profiting from that line, it will usually not move. People who have information will disguise their flow, they won't bet with places that will move the line against them when they bet (if you bet this with Pinnacle, for example, they will work out you are beating their line immediately, they have quants who can work out how you are beating their line, and you have permanently destroyed your edge) so you put money down at soft book somehow and they will likely not move line against you...meaning the line doesn't move.

Again, it is fairly common assumption that people make that it must be noise traders who are incentivizing syndicates. This is the case at open but not after, and there is a significant distinction between noise traders and noise traders through retail books. Retail books do not set the lines, they do not post lines early to syndicates, their product is completely different. There is literally no incentive for accurate prediction because the economic gain from noise trading does not accrue to anyone who has information. 95% accrues to firms with the greatest marketing advantage, again...this is entertainment, it is not about accurate prediction, you are misunderstanding at a very fundamental level what is going on here. It is like going to see the Minecraft Movie and thinking this is artistic expression on the level of Tokyo Story.

This would all be different if there were real markets underpinned by economic demand for this risk but there isn't. This is why Betfair failed. This is why these "prices" you see aren't actually real prices.