In most places the CBS was the worst attended meeting. If you were going to eliminate anything, that's the one you had to eliminate. Plus, it really didn't make them any money since very few contributed there and caused extra work. I'm still convinced they "combined" the midweek meeting for 2 reasons:
1) To allow the stacking of more congregations in KHs (less weeknights to schedule= maximizing the # of congregations you can fit)
2) decreasing # of elders to conduct.