I know what they are, and when they fail it's either a more time consuming or more expensive task to repair/replace (your choice) than the 10 minute swap external regulator.

I have 4 birds here, two have Delco-Remy external voltage regs, one has a '69 internally regulated alternator, and the other has a more modern replacement part...seems quite reliable to me since most people didn't go back to the dealer for replacement parts when cheaper options are available.