On the flat stages it's more a matter of teamwork to get someone back up to the front. E-E are pretty crap at regaining time on the flats anyway, and with the peloton's rush to be first across the cobbles and to be able to pick your own line, they got dropped. As did Hushovd and Moreau.
Euskaltel and Agricole were working to get back, but everyone else behind the split had their GC candidates up the road and therefore didn't have to chase OR work. Which is why you saw USPS' Noval sitting in the orange train, sheltering in the draft.
The same would have happened had Mayo punctured. It's up to E-E to get him back. Unfortunately the artificial barrier of the cobbles forced the issue.
When the race gets to the mountains and the fight for GC becomes more mano-a-mano, then courtesies become more apparent.