Advertisers won’t be required to use CBO in their Facebook ad campaigns. It is no longer mandatory for advertisement campaigns.
Campaign Budget Optimization (or CBO) means that there is a total budget for all your ads. And Facebook automatically distributes the budget to achieve the best conversion rates by tracking the performance data in real time.
Even though Facebook still believes that this option is the most beneficial for advertisers, they will give advertisers the possibility to choose whether they want to use it or not.
It seems like companies who have been testing it wasn’t really satisfied with CBO, and their opinion was heard by Facebook. Previously, Facebook planned to diminish ad-set budgets by September. We only can guess whether CBO becomes mandatory in future or not.