Anyone can say 'I love you'. 'I love you' doesn't take any effort. Someone could easily say those words, then turn around and cheat on their spouse. 'I love you' is really just a string of words that we as a society has agreed upon to verbally communicate affection, but what significance does it have when that is the extent of your affection. 

Often, nonverbal communication is much more effective at conveying emotions and intent than is communication through the verbal channel. For example, you could verbally communicate, "fuck you!" But the intent of that verbal cue could be drastically different depending on what non-verbal cues come with it. If you it is paired with an angry, red face, the intent is negative. If it's paired with a laugh or a smile, it's a positive. It's the same with, "I love you."

Words only have meaning when you have actions that correspond with it. It's easy just to say a few words and be done - but showing those feelings in our actions every day is much more difficult.

 If you truly love someone, you will never need to tell them.