The upper castes are not 'blind' to the situation. It works to their advantage to keep the status quo. If the downtrodden move up in life then they will be competing with the upper castes for education, jobs and in every sphere in life. Not something they want. Of course, I am generalising here!
Again, thanks to the local culture and religion. One's birth is accepted. If you are poor and deprived it is because you 'deserve' to it, thanks to your actions in some previous life. People are so thoroughly brainwashed into believing that the caste structure is gospel truth.