Another way to view it is that human rovers must go fast, because humans are impatient. We could build a faster, battery powered robotic rover if we wanted, but

Another way to view it is that human rovers must go fast, because humans are impatient. We could build a faster, battery powered robotic rover if we wanted, but why? If it's simply mileage you want, Curiosity's RTG means it can just keep going for years. With an average speed of 30 meters/hr, I'm not seeing much reason to think that it wasn't capable of covering ~1000km over those 4 years (the LRV, on the other hand, could never exceed 92km, total, before the batteries ran out). But mileage simply wasn't the goal.