Why is the plan to start off with so many fragile, resource-greedy people before the planet is improved? Wouldn't it be better to send a robot factory capable o

Why is the plan to start off with so many fragile, resource-greedy people before the planet is improved? Wouldn't it be better to send a robot factory capable of building more robot factories using materials available on Mars and minimal operating oversight (possibly combined with some plants and bacteria)? People could possibly move there much later after we've mastered the really complicated mining, geoengineering and farming problems needed to sustain people there.