[HerenIstarion]

Alaksoron

And why, praytell, are we not obliged to serve the elves?

Do I sense the touch of ridicule or is it genuine curiosity? I am inclined to judge it as an expression of curiosity, nevertheless, and answer your query to the extent I'm able to

Men are not supposed to serve elves on the basis that both have separate Eru-given functions of their own, their inclusion into the Ainulindale and following that, into being, being His unaided, detached contribution. Those functions are defined at their best in a conversation of Andreth, mortal woman of the F.A. with Finrod Felagund, which runs as follows:

Athrabeth Finrod ah Andreth

Andreth:

This much only can I say: that among us some hold that our [mortals - H-I] errand here was to heal the Marring of Arda, and by making the hroa partake in the life of the fea to put it beyond any marring of Melkor or any other spirit of malice for ever

Finrod:

'And then suddenly I beheld as a vision Arda Remade; and there the Eldar completed but not ended could abide in the present for ever, and there walk, maybe, with the Children of Men, their deliverers, and sing to them such songs as, even in the Bliss beyond bliss, should make the green valleys ring and the everlasting mountain-tops to throb like harps.

or, to quote myself from elswhere:

H-I

The brevity of their [human] life span in later works is associated with the Fall (as a race), for "wise among men" hold that in the original design Men were meant for life indestructible - union of fëa (of Eru) and hröa (of the matter of Arda) so unbreakable that it would be able to lift, bring up the matter, i.e. thing temporal, to the eternal world of flame imperishable. (elves in this scheme are supposed to function as a kind of memory cells - to remember and remind others of the first world, when the Arda Remade is brought into being) But men are so weakened by their fall that death is given to them as a release

and

At that, Men and Elves are direct insertions of Eru, Eruhini, his children, the whole mode of being of which (i.e. union of eternal fëa with temporal hröa) seems to be symbolic, indication of future arrangement, when matter will cease to be temporal and be equally eternal, and seems to set the direction of they development. At that, they have distinct functions - elves of preservation and memory, men of working future order out

Such distinct functions never imply servitude as an obligation. That some men may enter into the service of some elves, is obvious - but it would be out of respect, love, affection, even political purposes (Ulfang the Black and his sons Ulfast, Ulwarth, and Uldor), but not some kind of inherent, innate obligation

And hence the title - Elf-Friend. If humans were obliged to serve elves, the term would have been different, for friendship presupposes free will of both (or all, if there are more than two involved) parties - one can not be someone else's friend by force.