As i already knew, MP3 has 5.1 capabilities, and as Gabriel said:

"Mp3 HAS 5.1 capabilities.

There is no software using this feature now, but it is part of the standard."

WHY oh WHY, oh WHY? Please tell me why...

There is a program, the jukebox from creative ( Playcenter ) can read AC3 files with 5.1 output...other's i don't know

Mainly because big companies were not interested in.
Only Philips was interested in multichannel, and they created mp2 multichannel encoders.

As mp3 was created mainly for streaming over isdn lines, 128kbps was the target, and there was no interest in multichannel mp3.

The open source developpers didn't developped it probably because most of them do not have multichannel audio installation.

Damn this sucks... .... ..

...also there is no real source of 5.1 music (not talking about films), until DVD-audio takes off that is.

Yup that's true our 5.1 sound card's only separate the channel's from only 2 real channel's and choose the output to that 5.1 channels ( I think)