Simple: because you want the GM to have the bad guys have stuff armored enough to require your use of Demolitions to place the charges right for that extra damage.
Which probably means some form of mad scientist villains.
To be clear - I'm not trying to be snarky. Your skill choices in SOTC are cues to the GM. A SOTC GM who isn't challenging the key skills, or is avoiding allowing opportunities for them to matter, isn't really grasping the nature of the intended narrative mode of SOTC. Characters are supposed to be pulp Heroes, so it's their areas of skill that should be challenged most.
So, if you take pilot, and the GM makes certain you never get near a plane, he's already rejected your concept and not been kind enough to tell you.
Same for a dem-tech and things to blow up.
Further, as Tetra noted in the comments, your skill choices dictate how something gets narrated. Using Engineering to take down a bridge is different than using Demolitions or artillery.