Some thought that when a guy sings for her girl is because she forces him to do it.
But in reality, sometimes it's just another way to show her that she's loved and appreciated besides the casual "I love you" speech.
I might not be the best singer out there nor I have the most angelic voice but I don't mind to spend a lot of my time and effort to compose a song that's uniquely made just for her.
Every time I sing for her, I noticed the sparkle in your eyes, how much excitement that she had. Also it amazes me that she could memorize a few parts of the song even though she only heard it once.
So, I hope she'll join me the next time I sing for her.