Initial manned missions anywhere will never depend on in situ resource utilization, like soil, anywhere. And they will also assume that the environment is toxic until proven otherwise. You want redundancy to ensure that when things go wrong, which they will, it doesn't necessarily mean everybody dies.
Of course though you're completely right that mapping out the rough surface and climatic patterns is critical, but that would have been capable with the first probe to Mars - launched some 53 years ago. There's just really extreme diminishing returns with probes and rovers. For instance these [1] are NASA's highlights for what Perseverance, the latest Mars rover, has achieved in 4 years. To call them uninspiring would be an understatement.
[1] - https://science.nasa.gov/mission/mars-2020-perseverance/scie...
This is because there are increasingly fewer big discoveries to be made. No, an astronaut with a shovel won't excavate a lost Martian city, it'll be more of ISS science but in gravity and with sanitizer smelling dust.
We haven't even realistically begun to explore Mars. There are vast underground cave systems, it's still unknown what lays under the moist surface areas, and so on endlessly. Heck, we haven't even been able to expose subsurface strata. Even searching for metal deposits will be extremely important. But these are things we can't realistically do with rovers anytime in the foreseeable future.
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