Mr Scott said:
Depends. What you purchased is called a to first to last "Concept Album" which is generally listened to first to last track in order. However this is not necessary, Pink Floyd's "Comfortably Numb" is from the album "The Wall" but it does stand on its own as a single.
Many of my favorite artists have released concept albums: "Pink Floyd", "King Diamond", and "The Dear Hunter." However many of their albums do have songs that stand on their own, which are released as singles. I hope I helped your understanding of the music industry.
Condescension aside, all you've really done is state the obvious. All bands need to release singles from their albums in order to get people listening, and they tend to choose the best songs from the album as their singles because it's better to put your best foot forward. Further, each song needs to be able to stand on its own, because that's how songs work. This is just plain logic. There are comments that could reasonably be made in this thread that would be informative on the music industry, but I'm afraid yours were not them.
OT: Another album I like listening to as a whole is Sixx AM's
The Heroin Diaries. I don't think there's a single mediocre song on it, which is especially impressive when you know it was basically done as an afterthought to help promote Nikki Sixx's book by the same name (which I have yet to read, but it's around here somewhere). Basically, each song represents one month on the way from addiction through rehab to recovery, from a first person perspective. It's really something to listen to, I recommend it.