Considering that testing time was so limited, surely any time spent in the cockpit, on track is beneficial - even on tyres of different compounds?
Lazy Drivers
I hear what you are saying, but IMO, the other drivers were lazy.
Vettel is the just consummate professional who leaves no stone unturned. If I were a driver wishing to achieve greatness (eg. Alonso/Hamilton), I would be doing anything and everything to upstage Vettel. There is absolutely no way that I would be prepared to allow Vettel to get 1 day's extra testing time (even if the tyre compounds are different). If Vettel got even 1 hour inside a car, I would be kicking up a fuss about that extra hour. I'd want everybody around me to know that I mean business. I think its probably more psychological than anything else.
I would also take the opportunity to give Pirelli MY feedback and urge them to produce the tyres, the way that I would like. Whether they do this is not important. The point is that I would want Vettel to know that I'm not going to let him beat me off track and gain any strategic advantage. It's a psychological and possibly, a strategic game (if Pirellis end up creating a tyre, based on my feedback).
Vettel, Prost & Senna
In 2009, Hamilton/Alonso would've beaten Vettel had they been in an RBR. But this is no longer the case and if you want to beat Vettel, you cannot afford to give him even a 0.5% advantage.
When Senna entered F1, he was obsessed with beating Prost. He was not interested in beating anyone, except for Prost...as he believed Prost was the best driver ever. He would track him all the time and ensured that he didn't allow Prost to gain any advantage (off-track or on-track). IMO Alonso/Hamilton have to start giving Vettel the same treatment as Prost got (from Senna).
In any case, the way things are looking, Vettel could well become the daddy of F1 by the end of 2012 (some may argue that he already is) and beyond the reach of Alonso/Hamilton...it really depends on whether Vettel can improve or not. If Vettel does improve further, even if he doesn't gain a strategic advantage (off track), he may still obliterate the opposition.