The reason the astronauts flip the switch to start them: "The experiments could not be made fully automatic because NASA policy requires that experiments on manned missions involve the crew." Politics, again.
Kind of a tautology isn't it? The crew must flip the switch because on manned missions the crew must flip the switch. Why not send up unmanned missions
Which doesn't change the fact that a human overseeing an experiment can do a better job than a machine, and could cause the experiment to not be lost in the first place.
Due to the versatility and adaptability of humans.
No, but it does change the fact that humans are likely to lose their lives in the pursuit of the experiment. Losing a machine is merely an inconvenience.
In case they have all the tools, spare pieces and the knowledge to debug and fix the machine. And in case that the fixed machine is safe, for example if you forget to put a bolt and now the system is not tight and some of the fumes escape, or it begins to spin or make vibrations. There are a lot of possible problems, and having the middle of the space with no escape pod is a bad place to try to be creative.
The reason the astronauts flip the switch to start them: "The experiments could not be made fully automatic because NASA policy requires that experiments on manned missions involve the crew." Politics, again.