To elaborate on what Jon said, there are a limited number of metering slots available; the buses consume quite a few slots (56 -- 48 for input and 8 for output), so once you go above 8 busses you use up all the slots, and any further meters are inactive.
The question is -- do you really need 10 busses; often we find that people are using busses when they are not required; if you can drop back to 8 or fewer busses, you won't lose the meters...