Why aren't all digital albums split into 30-second tracks then?

Bands can always follow the King Crimson model, established on their debut album: dividing a long track into separate sub-headings within the song title ("Epitaph, including March For No Reason and Tomorrow and Tomorrow", so forth).

Said Robert Fripp: "The reason songs and pieces acquired separately titled sections...was so the group would get paid full publishing royalties on our American record sales"

But maybe that practice doesn't apply in our digital age?

Ditto. It might cost them some money, but is their decision to make them that way, and is not our problem if we like them as such. 

You do see some longer songs get split up thanks to the digital age - whether that's a response to listening trends of the younger generation or a desire to make more money depends on who you ask. Thick As A Brick and A Passion Play are now sold with separate tracks for each 'movement'. I remember listening to Suite For Flute and Jazz Piano Trio on Spotify and not only were the movements divided into separate tracks (which is standard practice for classical music), but some of the movements were split into two tracks, which I could only assume was for increasing the play count for royalty purposes.

I don't have a big issue with tracks being divided, just as long as the audio player will play them seamlessly - although I do prefer a single long track. I mean, most people who would take an issue with a song being divided probably wouldn't be caught dead listening to music on shuffle either, and that's really the one case where it makes a difference.

Unfortunately, as much as we call it progressive rock, the world of rock/pop has not really been progressed by it to embrace the idea that a song can be as long or as short as it needs to be. I still see music studios that will charge bands based on the number of songs... Hmm, I wonder if they'll let my band record a 20 minute song for the same price as a 5 minute song.