Of course they don't want to join; why would they? Bitcoin is a direct threat to them so they're hardly going to promote it to the masses to potentially quicken their downfal.
Right or wrong, the banks do not see Bitcoin as a competitive threat. All they care about is reducing their risk of being investigated for money laundering.
At this point, this is a conflict between Banks and Bitcoin on one side and government (law enforcement) on the other.
The fact that money laundering is a crime is the anti-liberty ("minority report") problem here.
Whenever the government cannot prove the primary crime (that one party has criminally harmed another), it cages the party it doesn't like for phantom secondary crimes such as money laundering, conspiracy or tax evasion.
