One reason Mars rovers travel so slowly is because they can. Being able to take all the time you need is an advantage, since it reduces power consumption and risk. It's a dead planet (as far as we know) so everything they're studying will still be there.
If there were an important reason to move faster, they would have built something different.
Another far larger reason why they travels so slowly is because of power constraints. It takes a lot of rocket fuel to deliver a significant payload to any interplanetary destination and both batteries and RTG's are prohibitively heavy at the kinds of wattage required for a pace that goes beyond that of a snail.
It is difficult to overstate what a limitation this has been for research there. Even without the benefit of a vehicle, a human walking at a natural pace would over a year be able to cover a larger region than all of the previous rovers sent combined across their entire lifetimes.
Well yes, but if they actually had the payload capacity to get a human and their supplies there, would batteries and RTG’s still be prohibitively heavy?
With fewer constraints, they would have built something different.
That's a good point but humans would easily beat out the utility of any probe if we get to that capability. It's not just a question of mobility and manual dexterity. We do have very capable robotics. The even bigger factor here is light lag.
Even if we don't bother landing humans on Mars, it would still be very useful to have some in orbit to be able to have a real time feed on the ground as opposed to anywhere between the 3 to 22 minutes (one way!) delay that it is from Earth. While our automation is getting better, it is nowhere close to matching that of a human scientist for at least several decades yet.
Yes, the lag is very limiting, but on the other hand, the scientists can go home to their families after work, rather than being away from home for many months. Or maybe work from home? That’s gotta make up for a lot. Scientific experiments often take a lot of time and patience anyway.
There are some mild improvements to autonomy. Apparently this rover is somewhat more self-driving? The helicopter apparently won’t do much, but maybe on another mission it will.
If there were an important reason to move faster, they would have built something different.