Thousands of years ago, the leader of all the elves formed an alliance to serve the human in the age of 10 in order to pay the cost of saving him and his tribe.
Most agree with the elf leader's actions, but some disagree. Some elves continue to distrust humans because they are skilled at betraying for their own benefit. They made their decision by majority vote.
Those who disobeyed their master's orders would have their heads blown off. Because of human kindness, elf trust in humans grows, despite the fact that they are capable of lying.
Following the alliance, every human and elf successfully made a contract, master and servant.
All of this is planned by humans. They take advantage of the elves trust.
And the end result was disaster. Most humans treat elves like dogs, but there are rarely respected in the same way that elves respect humans.