The problem is meteors are essentially metamorphic rock resulting from the entry into our atmosphere.

The reasons for a Sample Return mission to Mars is to retrieve pristine examples to study the dust and rock composition and to see if life in the form of bacteria exist in the Martian "soil", so it makes some sense before sending people. It is a risk adverse strategy based on the idea that we as humans shouldn't die and Mars is a bit to far for us to reach. This is a very pessimistic view based on nothing sensible. Plenty of people have taken longer journeys (in time) and with little food and no means to contact home or others. True many died and some didn't come back sane, but we are explorers if nothing else. Life is risk.