Yes, there is no monetary compensation. But the currency here is community service. If your CV lists you as reviewer, program chair, technical committee on XYZ,

Yes, there is no monetary compensation. But the currency here is community service. If your CV lists you as reviewer, program chair, technical committee on XYZ, it makes you look important. And you get to see very early who in your field is working on what. It has networking effects and you get to know people (other reviewers and committee members). That's why academics do it. Most of them anyway. All for "free".