Why use something different when what is being use works so well?
Because it is too difficult, time consuming, and expensive to come up with new designs when old ones will suffice. It is very smart and economical for a designer to reuse designs when his creativity and powers are limited. Since designers cannot just invent new designs on a whim nor collect the necessary resources for new product design and development, reusing old designs is a necessity.
But I agree. There is nothing in the Bible to suggest that the creator had unlimited intelligence or unlimited power, so it is very likely that such a creator would be forced by necessity to reuse designs to meet its 6 day deadline.
Progress in human affairs has come mainly through the bold readiness of human beings not to confine themselves to seeking piecemeal improvements in the way things are done, but to present fundamental challenges in the name of reason to the current way of doing things and to the avowed or hidden assumptions on which it rests. -- E. H. Carr