The FIA offered the amnesty, it wasn't demanded by the drivers.
Now ask yourself, why did the FIA offer an amnesty to the drivers?
Because they only had one target in mind - McLaren.
Now compare this incident to the way FIA handled other incidents where intellectual property was at risk - Ligier turning up with an actual copy of a Renault car, Shadows v. Arrows etc, - and you have to ask why didn't they do what they have done before, ie let the civil courts decide.
Clearly, FIA/Max Mosley wanted to put McLaren out of the running this year. Had Max had his way, they wouldn't have raced next year either, but that would have put McLaren out of business completely - but in a way whereby Max could have looked innocent. (Their sponsors wouldn't have extended the contracts, and without revenue, McLaren might as well pack in. This would hand Formula 1 to Ferrari for the forseeable future.
It also explains why they weren't banned for next season - people recognised that the consequence of making the punishment even worse.
McLaren wouldn't take such a situation lying down though. They would have appealled- either win an appeal or go out of business, being the choice- and the whole can of worms would have been opened up and FIA hung out to dry.
This demonstrates more than ever why Max Mosley is not fit for the post he holds, and why Ferrari have too much. Not only has he brought substantial discredit to the organisation, once again he has brought it to the brink of legal meltdown.
The man has allowed his vendetta to spiral out of control.