I wouldn't be too sure that it was restricted to the upper class, or WASPs. I'm of Latin American descent, and I remember quite vividly growing up in a then-largely Italian neighbourhood in Downsview and for occasions like nice dinners out, church, school functions, etc. even working class Italian, Argentinian, and Portuguese men of my father's pre-boomer generation put a jacket and tie on (and expected their sons to do the same) so I don't buy that argument at all based on my experience. I've seen pictures from the mid-late 1960s, just before my parents left Argentina, where the crowds at soccer games had many men in ties, and when they flew on Pan Am in 1968 to Australia all the men on the flight were formally dressed (and my parents were the farthest thing from wealthy, many people had co-signers for airline tickets in those days).
The men in jackets and ties at Leafs games in old photos were far more likely to be middle class, or even lower, than not. Even working men had at least one suit they put on to the rare treat to a restaurant, or a hockey game, or what have you. Dressing up is what made these occasions even more memorable. That was what was expected, both formally and informally. This goes back to what I said earlier that even "mundane" occasions prompted people to dress up for them even into the era when I was growing up (late 1970s), and not down which is the case now. Also take a look again through the Then and Now pics, look very carefully, and you'll see even into the 1960s men engaged in professions as varied as shopkeepers, bartenders, butchers, clerks, etc. all formally dressed, to say nothing of how much more formally dressed TTC motormen and policemen used to be. Suits were cheap, very cheap relative to income back then, and so to say that only upper class men dressed formally is false, when some street scenes from those earlier eras show *everyone* dressed formally, unless we're saying that no one beneath a certain income level ever stepped outside or happened to ever be photographed. Even Mad Men shows this if you pay attention to the background.
This entire notion that you "put on your best face" when stepping out of the house is almost completely gone now. I saw a Collector at King station yesterday who wasn't even wearing *socks*. When my dad started at the TTC in 1973 that would have been inconceivable, they only *just* got rid of the requirement to wear hats, so there you have it.
I have no dog in this golf course fight, as I don't golf and don't care for it, but I can't say the expectation of having at least a collared shirt doesn't surprise me at all. I suspect the requirement is something based on a combination of inertia, self-interest, and a lingering sense (hope?) that maintaining *some* sense of decorum will prevent a slide towards shabbiness and outright vulgarity and thus maintain the appeal and solvency of the entire enterprise.