Wow, music is changing and it reflects the times as well. I've noticed it especially recently though it has been happening for a while but albums are just getting shorter and shorter. There are many reasons for this and many that have been heard before so I'm probably not exactly going to contribute any new ideas to this but here goes anyway.
The MP3 format and the fact we can now pick and choose what songs we want and then discard the rest in the metaphorical digital bin from places like iTunes and that that I guess it makes no more sense for artists to create an album with 'fillers' but for me those 'fillers' was what made the album as well and one person's idea of filler doesn't necessarily equate to another. I have many 4 and 5 star songs that a lot of people would consider to be crap tunes and rubbish but I say the same thing every single time, music is always going to be heavily subjective. I suppose people have fooled themselves into thinking you can have a 'good' and 'bad' song and there are certain qualities which make that so but for me, music is all about what is appealing to your ears. That ear worm of a pop tune that nobody you know seems to like but you yourself gets to number one on the charts yet no matter where you go or the reviews you read everyone slates it as a bad song but hang on, what defines a bad song? Surely the fact that it got to number one alone means enough people liked it to send it there? (Of course this is not counting the overexposure of certain songs or because it was featured or associated with a certain show/film/etc).