From what I understand, editors have seen so much really, really bad second-person erotica that their hackles rise at the first "you."
I can understand that, in theory, second person POV seems more personal, more intimate, in a genre that's banking on intimacy, but readers are perfectly used to stories told in first/third, and can make the necessary connections if the writer is doing her job well.
The other POVs (first/third) also have the advantage of allowing the reader to maintain whatever distance she needs. Especially in erotica, despite its subject, sometimes the reader doesn't necessarily WANT to be too bonded with the POV. To use a somewhat controversial topic -- rape fantasies exist, and there are erotic stories using that fantasy, and some readers may find them arousing, but may, nevertheless, not want to identify too completely with the character being raped. The reader may not want to be told "you" are being attacked even if, to some degree, she is identifying with the character being attacked. Sometimes a little distance is good.
JD