That brings us to the question of reincarnation then .
you see, people dont care for animals because their mission is already complete. they already have peace on earth.

us humans are still realizing the material world for our higher intellect needs.
With any creature on this planet, it's goal is to survive and reproduce. It's goal is to help the survival of it's own DNA. Animals go about this a lot diferently from humans as they can't act out on their instincts as much as humans can. This is because humans have higher intelligence and higher capabilities making them more susceptable for survival.
There may be a point in time where we realise the materialistic world (that's to say there is a finite amount of physical knowledge in this universe) but it's only due to our survival instincts. We continually advance in technology because existance is a competition and competition always brings out the best. This is why we will continue to advance until there is something preventing that (whether it be cataclysmic destruction or the limit in knowledge).