Why doesn't the music in Minecraft play all the time?

The main point of the occasional nature of music in Minecraft is to build atmosphere. Minecraft is a, somewhat, lonely and isolated game (if you're not playing with tons of people yelling over Skype) so the game tends to be quite silent and atmospheric. There is no way to make the music play all the time since the sound design of the game is created in such a way that music plays at certain events, whether it's combat, nightfall or a sunrise. To look at it a different way, Minecraft is supposed to be, actually, a really creepy game (and if you are playing alone, it certainly is). So that answers the question of why Minecraft music is not playing all the time (of course, including colorfusion's answer about the technical limitations). As far as making it play all the time - no, you can't. I've searched for mods that do that to no avail, unfortunately.

That's just the way Minecraft was made. Presumably, the short bursts of music are to add to the ambiance. Short of mods or an external media player, I don't believe there is a way to make music play all the time.

Try it with a Command block...

/give @p minecraft:command_block

In the Command Block:

/playsound "Folder" "musicname" @a

Command block: set to 'Always active' and 'Repeating'

You could also just look up the Minecraft soundtrack on youtube and have it play while in game. If this makes your game slower, then set the quality of the video to the lowest choice. I run a pretty old Mac and this seems to work for me! Hope it could help.

Here's a link to the Minecraft OST in a Youtube "Playlist" form, so it'll play through all of the tracks in their entirety. You can also right click the video while it's playing, or double-finger click on mac, and select "Loop" to loop the song on replay.

If you can play that while you're playing Minecraft, you're good! Just go in to the game options and find the audio settings. There you should be able to turn the Music all the way down in game while you listen to music. Me personally, I have a PS4 hooked up to the tv. I'm sure there's a way spotify Minecraft music, but I'm not a Spotify guy, so I use "Remote Play" to play ps4 games on my laptop. So there, I open Youtube with the link above and play PS4 Minecraft on the same device. Very convenient. I understand though, people will have their different reasons for this. Some may want to send the audio signal through different devices or one single device. This isn't an option for everyone. It could help some people though. Hopefully_