Well 4/6 come inside the jewel cases for other games… they can be obtained by buying those games.
You have information on things like the never released FFIV for NES - nobody can obtain that either.
I’m with you on being against including non-video game material on this site, but I think these demos are relevant.
For the record, these came out since the PS1 generation:
-Final Fantasy XI - Online [PS2 Beta Version] [Disc1of2] SCUS-97271
-Final Fantasy XI - Online [PS2 Beta Version] [Disc2of2] SCUS-97272
-Final Fantasy XI Online PS2 demo SCUS-97380 2004
-Square Enix Sampler Disc - Volume One SLUS-29087 2004 Square Enix
(exclusive giveaway for pre-ordering Drakengard at Electronics Boutique and Gamestop in January and February 2004)
-Square Enix Sampler Disc - Volume Two SLUS-29098 200 Square Enix
(ordered online from official webstie - Front Mission 4 demo only)
-Final Fantasy XI Demo Beta (Xbox 360) February issue of Official Xbox Magazine 2006
-Final Fantasy XII Demo (included with Dragon Quest VIII)