Not many events require even the most basic ceremonial dress nowadays. You can be a pall bearer in jeans, get married in a t-shirt. People do it all the time.
But graduation from college, with the years of efforts and boatloads of money, robes and special hats are still in order, and while I haven't done a study, I'd be surprised if one student in a thousand fails to fall in line, despite being young, a period otherwise associated with nonconformity.
New York University scrubbed their in-person graduation, but sent my older son a charming velvet cap. There was something vaguely Florentine about the flat, eight-sided flat hat, it spoke of courtiers and dirks thrust into knee socks,. I delved a bit.
The cap is called a "tam," and is the traditional headwear for doctoral candidates, as opposed to the undergraduate mortarboard and tassel. A law degree is technically a doctorate, "juris doctor" or "doctor of jurisprudence," though lawyers mercifully do not use the title "doctor," for reasons that are murky, a law degree being about as difficult to achieve as, say, a doctorate in education.
Despite its Scottish name, the academic tam is not descended, stylistically, from the Scottish cap, but from the Tudor bonnet.
There was no entry for "tam" in my Oxford English Dictionary, but I dimly remembered that "tam" is short for "tam o' shanter," and there is an entry for that. "In full, tam o' shanter bonnet cap," the Oxford explains after letting us know—to my surprise—that it derives from "the name of the hero of the Burns poem of that name (i.e. Tom of Shanter)."
"Tam O' Shanter," a tale of drunken camaraderie, and was rewarded with a number of sharp lines. It begins, perhaps oddly, reflecting on the wife at home, growing angry:
We think na on the lang Scots miles,"Nursing her wrath to keep it warm" seems a handy phrase to have in your back pocket.
The mosses, waters, slaps, and stiles,
That lie between us and our hame,
Whare sits our sulky, sullen dame,
Gathering her brows like gathering storm,
Nursing her wrath to keep it warm.
It gets murkier from there. Tam is, in his wife's estimation, "A bletherin, blusterin, drunken blellum" ("blellum" = "a lazy, talkative person"). After drinking away days at market, he blunders home. He looks into a brightly-lit church, at first hopefully, then finds some kind of grotesque festival of witches and warlocks and the appliances of murder. He finally makes it home, thanks to his intrepid horse Maggie.
"Now the milliner's name for a flat broad hat, based originally on the blue bonnet of Scotland," the Cornhill Magazine wrote in 1890, that "now" making it sound a recent development. Though I found a poem in Punch about the hat in 1880. Before then, the references I noticed were to the verse, not fashion.