They aren't meant to be perfectly well thought out, well at least in my opinion. They are included not to hand you the perfect rocket/plane/etc. to do whatever, but to give you an example and ideas on what you can do. Perfect crafts would just take away the fun and effort of designing and testing as you could just load up the perfect stock crafts. Now you've demonstrated yourself that they work as test crafts, to see what works and doesn't.