EDIT: Source: https://aviation.stackexchange.com/questions/61011/how-many-...
The triple redundancy only comes into play with systems with a severity of failure rated as catastrophic.
The MCAS system as originally designed was rated as merely hazardous. Which doesn't require redundancy. The decision to feed off of only one vane was intentional to avoid having to have pilots undergo level D simulator training as part of their type certification. Multi-sensor systems generally require Level D training.
See the 737 MAX Expose by 60 minutes, where the whistleblower testimony is first presented.
Somewhere inside Boeing there are decision-makers that lack ethics (or even long-term financial thinking). They need to be fired.
There's a Bloomberg article I've been trying to track down from back in the 2000's where a Boeing exec is quoted as saying that Boeing is going to undergo a financial transformation, part of which involved decreased "over thinking the box" and stripping all that wasteful effort (what engineers call the hard parts) from the process in order to bring Boeing into the mainstream as an optimized shareholder value generating machine.
This happened apparently shortly after the McDonnell Douglas merger as I understand it.
Specifically, because airlines wanted to save money on pilot training.
The more complex you make the plumbing, as it were, the easier it is to clog it all up.
Plus, there have been instances where a majority Ocala sensors have frozen in the same position, and outvoted the last remaining functional one. At the end of the day, software can only be considered an automation aid.
The human pilot must be able to make a reasonably safe go of flying the plane alone. Even Airbus planes have this quality in direct law. They are still stable, there are just fewer safeguards to keep you from doing something daft.
And even with airbus' approach, there's a case to be made that overreliance on the computer to safely operate the plane degrades basic piloting skills through atrophy or complacency.
Roughly speaking, stick force is the amount of force the pilot has to to apply to the stick to achieve a given movement of the control surfaces.
As the airplane gets closer to a stall, you want to make it harder for the pilot to pull it fully into the stall, by increasing the required stick force.
If the stick force decreased as the airplane approached a stall, then the pilot would have to actively push the stick back into more stable flight.
Autopilot? Not necessary, pilots can fly themselves. Still, it is added for convenience (and its consequences, less mental burden, more mental capacity to do other stuff).