Obi-Wan said:

Also notice: In the novel this scene ends with Hobbie's damaged snowspeeder crashing head on into General Veers' walker.

The storyline from the novel does not appear in the actual movie in which the Empire's attack is shown more dominant. If I'm not mistaken the crash is happening when Veers is aiming at the generators through his periscope when his vision is suddenly distracted by the attacking snowspeeder and its kamikaze course.

Well, Ady did say the EU is irrelevant for the purposes of this edit, and as for the novels go... Uncle Owen is Obi-Wan's brother.

Not to mention it takes away from the menace of the walker if they can't shoot something right in front of them, and reusing shots would be redundant.