This brings to mind an old adage about eggs and baskets. More seriously, adding extra components to a mission means many more man-hours designing, testing and

This brings to mind an old adage about eggs and baskets. More seriously, adding extra components to a mission means many more man-hours designing, testing and vetting the extra functionality, and also adds a boatload of extra weight, which makes the entire thing massively more risky and expensive (especially with the rover's at-the-time-unproven landing mechanism). There's no real need to send everything at once, especially if a lot of what you're sending could be ruled out as entirely unnecessary depending on the results of other tests you're carrying out.