Well, mainly because it's cool.
I mean, I know that us looking at some giant sign advertising "Burgers Let's!" may not seem like Coolsville to us, but it's cool for them because it's a different language. Believe it or not, Japanese people like American stuff, just like lots of us like Japanese stuff. It also makes them seem a little more intelligent, because it's in another language.
By that same token, why do a lot of anime fans use words like 'kawaii' and 'neko' and greet each other with 'konnichiwa' ? Whether we care to admit it or not, we consider it cool because it's a different language. And how many music artists use words from other languages in their songs just for effect or because it sounds different or cool? It's basically like that. It just stands out to us, because "Ai ravu yuu" sounds more like an exotic dish than a love confession.