A couple of quick points: Most rules can be enforced with a varying degree of strictness and I find that people expect to be able to enforce them against OTHERS perhaps more strictly than they expect them to be enforced against themselves. This is a variation on the German engineers, /English policemen/ French cooks idea. Thus, if you believe in the necessity of an association before you can wear a kilt, chances are, your ideas of how close an association is required might vary depending on whether it is a tartan you choose to wear, or a tartan some jerk just showed up in... I expect this is how the present state of affairs came to be.

Second, a person might adjust the restrictions and expectations a little when one considers the availability of the tartan and the breadth of its distribution. When you get serious, you will notice that a dozen tartans probably account for 75-90% of the tartan goods you will see. If every scrap of Royal Stewart and Black Watch tartan were to disappear in five minutes, there would be a lot of exposed flesh, not to mention picnic coolers, cookie tins, and luggage suddenly spilling their contents. If your name is Hunting Ross and you encounter someone wearing the Hunting Ross Tartan, you might be excused for expecting a connection. If you expect the same from every guy with a wax jacket lined in Dress Gordon... well, you get the idea.

I am willing to bet that some canny Scot will observe that owning just one kilt makes things a lot easier...

PS, wasn't there a "So, you play for the Mets...?" skit on SNL based on this idea?