Of course elf males exist, and of course the majority of relationships involving elf females are with elf males, just like the majority of relationships involving human women are with human men. This is to be expected for any race. That's not to say relationships between humans and elves don't happen though.
However, as a species that normally only procreates a few times over a lifespan of centuries, elves are adapted to extremely infrequent coupling, maybe a couple times a *year* on average. Curious elves who seek out a relationship with a human partner are often shocked and even intimidated, then, to discover that for humans a "healthy" sex life is several times a *week* (to put this in perspective - it'd be like a human finding out their partner needs to have sex hourly in order to stay satisfied). While elves don't have any difficulty *physically* adapting to keep up with this level of demand, the *mental* exhaustion of what, from the elf-perspective, must feel like literally *constant* sex is often overwhelming. This enormous gap in sex drive leads to the failure of nearly all monogamous relationships between humans and elves.
Most relationships between humans and elves that do last involve opening the relationship to one or more additional partners to help 'share the load'. In some cases, an elf will seek out other elves, typically siblings or friends from their village. In others, a mutual human friend may be invited into the relationship. This makes cuckold/cuckquean-dynamics almost universal in relationships between humans and elves, though not always the dynamics one might expect. In group of elves servicing a single human, it's actually the elf at the *bottom* of the pecking order who usually has the most sex, while the more dominant elves prefer to abstain and avoid the stress of 'excessive' coupling and may even manipulate or bully the more submissive members into enduring a greater share. In cases where another human is invited into the relationship the resulting dynamic depends on whether or not the elf is strong-willed enough to maintain a hold on the majority of their partner's attention and emotional investment: If so, the elf dominates and the new human (while well-treated and well-loved) is relegated to the position of a marital aid, and if not, the new human will quickly dominate the less sexually active elf.