If you have great legs, you wait for the right chance and attack, you don't chase down every attack, tow the group and then attack. There is no reason whatsoever to waste the energy.
Froome does it because he has never, since his transformation, actually been challenged and he has no idea how to ride while judiciously using his energy.
The point of all this discussion is as follows. You have a rider in Contador who everyone agrees is on the full sauce this season. Yes? And then you have a rider who can still beat him, wasting energy and using incredibly poor tactics. He has that much energy to burn. No one has ever seen someone ride like this.
The point of all this, and the strong undercurrent of the discussion is that Froome is beating a fully-doped Contador, and doing it while wasting power. What that means is that for one to believe he is clean means that he is riding with as much or maybe more power than we've ever seen, even in the height of the uncontrolled doping era, and claiming constantly that he is clean. His team claim to be clean.
We are trying to get the remaining people who actually believe this to see how absolutely impossible it is. No one can ride like this clean. We've never even seen people ride like this doped. It is a farce to claim cleanliness after putting on displays like he has the past 2+ years.