Not to offend, but I think it has declined because this naming of Jr, III, and so on has come to be associated with poor or rural people. For what it’s worth, I have a relative who is a IV
"Junior" might be associated with poor or rural people, but "III" and "IV" can only convey the absolute maximum level of pompousness.
(There was a brief period where my sister was dating someone who went by J.T. The initials were something of an effort to obscure his name, James III.)
Never heard that framing before. In New England the practice is associated with blue-blood wealth.