Groups such as Napalm, and hitmen dev (develope) demos based on the language that they have learnt etc, often releasing cracks/patches etc, these people are serious programmers, try looking up PS2dev on Google you will find tons of material, Hitmen have been releasing stuff for god knows how long, think in terms of the people that produced cracked compilation disks for the Amiga, or Atari ST...... same kinda stuff, here's a good link for you has some PS2 and PSX demos/intros etc, and even stuff for the SNES etc...
http://www.pouet.net/topic.php?which=8
This stuff is mainly people who 'learn'

the language and hardware that a console works on, and there is some great stuff out there......... (NES Zelda for example, that u can play on the PSX) (look at zophar.net)