The only reason supermajority is required in the current Senate is because a Senator can hold a "pocket filibuster" which in practice gives any single Senator the power to veto any legislation at any time for any reason for as long as they are in the senate. Were they to change their procedure and require Senators to actually speak in order to exercise a filibuster you would see this change pretty quickly. Strom Thurmond spoke for days to filibuster the civil rights laws, and he eventually had to stop because he got tired. He had aides holding buckets under the podium for him to relieve himself at times.