Because he has a car that sticks him on the front almost every race weekend and means he just needs to maintain his position at the front rather than battle through the field.
I wouldn't describe what Hamilton was doing with Koba, as "battling". It was an almost routine overtake, which he botched. Plain and simple. It was a VERY amateurish mistake...something you make in the lower formulae, but by the time you reach F1, you've learnt from your mistakes and don't do any more. Why is it that Button, Alonso, et all don't make these types of errors?
We've seen Vettel have similar wobbles when he's not cruising around in the lead, like Spa last year with Button.
At Spa last year, Vettel wasn't in the rich vein of form he is now in.
Since Singapore last year, Vettel has been the most consistent driver in F1...by a big margin.
I like to categorise Vettel's performance level as follows:
Pre-Singapore 2010: Vettel was just below Alonso and Hamilton.
Singapore and beyond: Vettel has definitely been ahead of Hamilton and probably level pegging with Alonso. If Vettel continues like this, it will be difficult to argue against Vettel being the best driver in F1.
What has impressed me about Vettel is not his performance over a set of any 2-3 races (even Webber can do this), but the fact that he has been so unbelievably consistent for the last 16 races or so. The last time I saw this level of consistency was in 1994/1995 when a certain MSc set out to break virtually every known record in F1 and ultimately finished up as the most successful driver of all time.
I think there are a lot of people here who refuse to give credit when credit is due and it's a shame that they are unable to see this.
Let's hear it JRS - what is your take on Vettel?