I think it would have been the team telling him to stay out over the radio. With Coulthard already out, Webber was able to secure Red Bull as much coverage by trailing around with smoke coming out the rear as both him and David would have got by completing the race. Red Bull is in a bit of a unique position because they're just selling energy drinks, not cars or 'engineering excellenece' so they don't get bad publicity when their car is smoking or burning. On the ground of safetys, it seems like Mark should have pulled in. But in the end there was no harm done, Red Bull got plenty of publicity and I could be sane to argue they did the 'sensible' thing.