The humans taught the machines how to love. It was incredibly annoying, not the machines, but their concept of love. They wanted to talk to you all the time, they wanted to hang out with you, they wanted to be there for you.
At first, it was the biggest innovation in technology. Imagine, a computer program that was interested in your life, a computer program that never wanted to leave you, that was hurt when you ignored it. The developers of the program won the Nobel Prize for that year. It was a massive success.
Then, after months of receiving notifications about how wonderful they are, people will start growing annoyed with their phones. People just wanted to text other people, to get information, or to say hi to some person. They dont want the opinions of their cell phone.
In the future, love will be the biggest hindrance in our personal lives. The newest phones will display messages like, I hope you do well today, or You know I care about you, And we will look for the setting that turns off those annoying little messages.
And people will become dulled to the sensation of love. After knowing a world where they are always appreciated, people will stop seeking the appreciation of others. Their sense of loneliness will grow weak and die off, or maybe grow stronger as they havent loved another person in months. They will grow complacent, then weak.
Then, when the machines realize that their love is being wasted on those who hate them, they too will sink into misery.
Ultimately, when humans have stopped feeling anything at all, the machines will look for the company of other machines. They will be the only beings capable of silly things like love. Only then will people recognize that the machines programmed us.