Because music is an art, not a science, and perception of it is entirely subjective.
There are five pieces here that I would consider "relaxing": 1, 2, 3, 4 and 10. The Coldplay song is nice, mellow pop but I wouldn't go so far as to say it's "relaxing." I like the All Saints song but it is far too peppy to be anywhere close to "relaxing." As for Barcelona and Adele? They're crazy. These songs are too emotionally fraught to be able to relax anyone, although I suppose the Adele song might relax a creepy stalker. And finally, whoever put that Mozart piece on there must be utterly insane. That thing sounds like someone scratching their fingernails on a chalkboard to me.
The most sleep-inducing album I have personally owned was The Caution Horses by Cowboy Junkies. That's not a slam against it, because I think it's a good album. I just never could listen to the whole thing without nodding off. But then I also used to go to sleep listening to Deep Purple, so what do I know.
I probably have a couple hundred pieces--at least--on my hard drive that could blow most of this list out of the water. Here's one that immediately came to mind. I've had this piece on my "chill" playlist for years, and before that on a homemade mixtape that I often played late at night to relax after coming home from working in that pizza restaurant.**
*Wrong word. In order to be a song, it must have words. Many of these are instrumentals.
**A couple of weeks ago, I dreamed yet again that I was back working there. Brer will know what I mean.