Benaphore is a kernel synchronization object behind atomic counter for uncontended path. But the kernel object needs to be always here, initialized and destroyed when appropriate.
Futex doesn't need any kernel initialization, and from perspective of kernel it doesn't exist at all when there are no waiters.
(see also CRITICAL_SECTION, which originally always had kernel object created with it, but it was later changed to create them on-demand falling back to keyed event on failure. SRWLock only uses keyed events. Keyed event only needs one object per process, and otherwise consumes kernel resources only if there are any waiters.)
Futex doesn't need any kernel initialization, and from perspective of kernel it doesn't exist at all when there are no waiters.
(see also CRITICAL_SECTION, which originally always had kernel object created with it, but it was later changed to create them on-demand falling back to keyed event on failure. SRWLock only uses keyed events. Keyed event only needs one object per process, and otherwise consumes kernel resources only if there are any waiters.)