@Grishka; sorry missed that you were only speaking of MIDI. So it's basically for synchronisation of parts; as in avoiding the harmony of the first complete bar being played under the anacrusis?

Although in the unlikely event that you were playing from a raw MIDI file, you would spot the first beats by the accents (or increased loudness) just as you would in a live performance (yes I know not always, I have sung madrigals!), so in that sense bar lines are redundant.

NWC deals with anacruses and mid bar repeats by requiring the next bar-line to be a double bar to reset the sequence, after which it fills them in automatically when told.