Again, I understand that in English, because there are so few ways of saying I love you (actually only the one that I know), it seems possible to overuse it. The fact that you can use it for food or things is unfortunate. In Spanish and the few other languages I am familiar with that would make no sense.
In English, I end many conversations with my close friends and family by saying, "love you, ciao." The odd thing is i can honestly say at that moment I believe it.
I love my brothers and sisters with such intensity that I can honestly say it all the time, and sometimes even in the middle of a fight.
But when you have ways of nuancing the word, it becomes more clear what you are feeling as you voice it. I can say to my ex bf I love him in a way that articulates how much I care about him, but am not in love with him (te quiero, in context it speaks to how I loved him and love in still in a way - although this phrase may usually be reserved for lovers). On an aside I have been dating guys since I was in the 5th grade and am friends with all of my ex's save one.
Another element may be the idea of neediness. Perhaps someone who comes across as needy and says, "I love you," frequently, may appear to be watering it down, or it may make someone appear needy.
Perhaps knowing the person helps to put the phrase in context and the nuances that are not explicit come out in body language, history, and that unspoken understanding of communicated between close souls.
Without making this about me, but to explain my thinking on this, I live life with a passion for people. I believe all my money and resources are for investing in my community. Everything I do points towards that work which is where my greatest happiness lies. When I'm not dating I don't feel alone as I know I am loved and respected and don't need one man to make me happy. So when I say I love you to my friends, it is a celebration of not only what I feel but a thank you for being there in my life.
I told one of my friends that my relationship with him was among one of my greatest achievements. I really mean that. I think love of any sort is the best achievement possible and just because there is lots of it does not mean that it is to be taken lightly.