I am thinking only a majority is needed to make a rules change. Usually each new Senate just approves and accept the rules from the previous Senate, and so on. But the Senate does have the option to make changes of the rules at the start of each new Senate session. Rarely ever done though.
Individual Senators like it the way it is. With the current cloture rules, every Senator is a potential swing vote. Makes each individual Senator more important, and generates lots of lobbying and goodies to get his vote.