"Well, I disagree, because she gave him something to think of when things got bad"
They could have used anything - childhood memories, for instance, would have broken up the plot less and served essentially the same purpose. And yeah, I'm sick of that instant-familiarity-"weird" girl shite too.
"And if you notice, 99.9999999999% of the movies released have some sort of romantic side to them"
Hell yeah I notice. I hate it. Unless it's a love story, it only distracts from the main theme (unless a significant portion of the theme is related to love - Kill Bill being an example). There are great works of art where the creators have refused to allow romance to muddle up their point - The Prisoner is the first one that comes to mind (I can't remember where I read it, but I know that despite all the women being written into the show as love interests McGoohan refused to allow his character to ever fall in love with one) - and there are plenty of others that just don't include it. Can you imagine if the Dollars trilogy had love interests? Gak, gak.
It's essentially because of this subplot that The Experiment feels like a German film made for the American market, just like all those ragtag knockoff cooking-based films but with a slightly hipper market. It ruins the entire possibility of the film feeling culturally fresh and bringing a newer way to check things out, and makes it feel like just another movie; above-average, but not great at all.