In a concert the environment is determined, starting with microphones, going through cables, mixers, effects, amps, speakers, and ending with the acoustic properties of the venue. What you get is a finished product, hopefully at it's best.
In studio work most of these factors are unknown, and the only reasonable choice is a compromise - the output must sound good through $2 IEMs on an mp3 player, in an elevator, a car player and on a high end audiophile system. On top of that there are individual preferences regarding volume level, tonal balance etc. Each of these environments and components colors the sound in it's own way. To have the best possible control over the final output, engineers tend to use components with possibly flat characteristics - that way you can have reasonably complex sound path without needing to worry about particular frequency suddenly booming or something like that.
Many audiophiles have pretty complex setups as well and then the choice of flat response curve is also very desirable - not because it is enjoyable to everyone out of the bat, but because it's easier to control it and tune it to their individual tastes and preferences.
HD800 fits this purpose quite well, but no one says it's the only option. If your needs are different you have choices - there are Grados, Audezes and others that have different characteristics.