Ordinarily this isn't a problem as most of the music I listen to comes in chunks that are somewhat longer than 30s. However, there are times when it means there are gaps in my scrobbling record.
Right now, I'm listening to a set of variations for piano by Paul Dukas (yes, he did write something other than the Sorceror's Apprentice!) and in this recording the theme and at least one of the variations (which are all on separate tracks) are too short to be scrobbled.
I've had similar problems with some of the recitatives in cantatas by Johann Sebastian Bach, amongst others.
I assume that there are good technical reasons why shorter tracks don't scrobble (it could be to avoid things like Spotify adverts - which generally seem to last 29s - from showing up in your listening history) and I realise that it's not the end of the world if I don't have an absolutely complete record of everything I listen to…