Interesting claim. Maybe you can give some examples to show High Elves always ditching humans at the first opportunity they get ?
Because my recollection of High Elf lore and characterization, based on the most prominent High Elven lore figures, is somewhat different.
Alleria Windrunner: got a half-elf son with a human who she still loves, even after hopping around the cosmos for a 1000 years. She also joined a human and dwarf army through the dark portal to another planet. To be honest that doesn't sound like ditching humans the first chance she got.
Vereesa Windrunner: got half-elf twins with a human husband (Rhonin) and sided with a human (Jaina) to kick Blood Elves out of Dalaran, a human city. She leads the Silver Covenant, a high elven organization, who joined the Alliance in northrend and has been (and probably still is) fighting by their side.
Sylvanas Windrunner: Allowed a human to join the High Elven Farstriders (Nathanos). Even though she is undead and no longer a High Elf she clearly still has feelings for him.
Kael'thas Sunstrider: was in love with Jaina (a human) and decided to team up with humans to fight the scourge in Lordaeron after the scourge had destroyed his homeland.
Anastarion Sunstrider: formed the first Alliance between High Elves and humans, allowed 100 humans to be trained as mages. In return king Thoradin (a human) helped the High Elves defeat the Amani Trolls:
"Assured that Quel'Thalas was saved from destruction, the elves made a pledge of loyalty and friendship to the nation of Arathor and to the bloodline of its king, Thoradin. Humans and elves would nurture peaceful relations for ages to come." -- source
Apart from these lore figures you have the story of Dalaran (human nation) and the Convocation of Silvermoon (High Elf government organization) forming the council of tirisfal leading to the first Guardian of Tirisfal, Alodi (another half-elf).
To me that doesn't read like High Elves
always ditch Humans at the first opportunity.