Because we have no earthly clue how to create and assemble all of the components of a cell ab initio. We're not really too sure about how proteins fold, we don't really understand what all of the genes and proteins do, ...

Like trying to build a car from ore without accurate plans.

EDIT: Wanna be a hero? How about stable batteries, battery recycling or room-temperature superconductors. All of these are tickets to fame, fortune, ...