Comment by gobdovan

There's also a (maybe more minor but still interesting) explanation. On a server, you know quite precisely your load and you want to be able to causally trace bottlenecks, which is simpler with AOT compiled programs. On users' machines, they may not give you full telemetry and may use your system in quite variable ways. So V8 comes in quite nicely and optimises hot paths on workload it observes on each users system.