People shouldn't think the randonneur rules were/are 'writ in stone'. It wasn't until 1966 that the PBP maximum time limit was reduced to 90 hours (previously 96) and support between checkpoints was banned.
Expensive 1200s will ultimately live or die by their popularity. If you will only ever do one 1200, the entry cost is almost irrelevant. If you do two or more a year, entry cost becomes a significant factor. First-time riders tend to want the security of more extensive support, rather than the 'go with god' approach. I would guess that most randonneurs only do one 1200...