BIAB is for creating your own backing tracks although as VideoTrack says you can download midis from the internet. There are even BIAB song sites where you can downlaod other people's versionsd of standard songs in the BIAB format. In fact, BIAB is not the best midi file player if that is all you want. RealBand would be better so you can more easily edit individual tracks.

But why should BIAB stop at jazz standards? why not country? why not pop? why not blues?

the list is endless and it's not really what BIAB is for. for $14 another company seems to have what you want sewn up - so why should BIAB get into markets it's not designed for?