If You Use CBO - why pause ads? Can someone explain this to me?

If FB is supposedly so smart when using a CBO that it shows right ad to right person - what's the point of pausing an ad in a CBO?
Wy not just let them run and add new ads as you go and if they hit they hit and if not they just get no impressions.

Normally, CBO is turned on automatically every camps

That's right, the CBO campaign can't shut down on its own, but it will cost less.

Jenny 15 said:

Normally, CBO is turned on automatically every camps

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