Generalisations are always wrong, but let's not worry about that. Secular music appeals to me much more than "Christian" music, with few exceptions. I listen mainly to rock and blues for excitement, sometimes jazz and ambient for chill-out, yes others. Rarely soppy ballads.
The answer to the question in the title is that he is not happy. Most great music - and don't bother pointing out the exceptions, yes there are great love songs - is produced by those who are seeking or weeping.
Off the top of my head:
Dylan's masterpiece, widely reckoned, is "Blood on the Tracks" about his marriage breakup.
Fleetwood Mac's "Rumours" is about the disintegration of two relationships.
Top of the Abba favourites list, according to polls, is not "Dancing Queen" or "Waterloo" but "The Winner Takes it All".
"Wish You Were Here" reveals the loneliness and alienation of Roger Waters in its title alone.
Songs about lost love, unrequited love, unattainable love ... you know them. It's well known that a great love song is much harder to write than a great song about lost love. "Goodbye to Love", "Without You" (I hate that one but it was number one for ever), "I'm Not in Love"...
So let's rejoice that Christians have trouble writing great songs.
[Ironical Postscript time: I was driving to College with the music turned up loud and the window open, as is my wont - Bill Wyman's Rhythm Kings. Generally full of happy songs, in contrast to the usual stuff referred to above. What came up as I turned into the College drive? "I Want to be Evil". Literally true.]