It's been over forty years since the last sample was returned from the Moon. Yet to this very day, Earth-bound scientists are managing to extract meaningful data from those returned samples. Those returned samples were and still are a treasure trove of information. This is what makes a sample return from Mars the holy grail of Mars exploration, much so than terabytes of data from a rover that is inherently limited in power, size, and analytic capabilities.
The devices we humans send to Mars are extremely limited in capability. There's only so much sense a scientist can make out of remotely sensed data sent from a limited device (e.g., a Mars rover). It's a bit of a matter of garbage in, garbage out.
Bringing back samples from Mars would be a game-changing event. This would enable scientists who are stuck on the surface of the Earth to have decades to make sense of those returned samples. As I mentioned above, scientists are still managing to garner information from the samples returned from the Moon. The same would apply to samples returned from Mars, in spades. (Soooory, I just couldn't resist the pun.)