There was absolutely no issues for US Passport holder to open FCNR or NRE or NRO account in mid nineties.

GUWonder point is right on the money. The change is more due to mushrooming of such transactions and removal of fear associated with anything "forex".

One disadvantage of OCI is that one has to undergo the brutal process all over again once you cross 50 and get new foreign passport. If someone is at age 49, I would strongly recommend waiting until age 50 to convert PIO to OCI.