Relationship Elves and Men

It accured to me, that every single interracial (pardon that expression but no better came to my mind ;-) ) relationship between Elves and Men is always kind of one sided. Specificly if you look at it from the gender point of view.
It is always a elv woman and a mortal men as far as I have read the books. Starting from Luthien and Berens over Tuor and Idril to Arwen and Aragorn. The elv part is ever the female part.
Maybe one of you has some kind of explaination.
I read once in a book of Irish myth that the men of the Tuath'an (an elv kind of race living under the soil or so of Ireland) regarded the human woman to be ugly and clumsy...

Thanks.