[_gfrc]

For me, there are two reasons:

1) The trains go every 30 minutes to Munich, so I don't have to wait that long.

2) The price structure of trains vs planes. The standard DB train ticket is flexible, i.e. you can use any train at the given date. Booking a flight on the same day is very expensive (and might be impossible if all seats are taken). There are discount tickets that are not flexible, but the price of the flexible ticket doesn't increase to enormous sums just because I book it on the same day - it's always the same.

[gpvos]

On the other hand, in my experience the cheaper inflexible advance tickets stay cheap for longer for flights than for trains. I guess it depends on whether you travel for business or leisure.