The right to wear a clan tartan

[Streetcar]

One of the themes that keeps coming up on these boards is the subject of clan tartans, and the right to wear one. I consider myself reasonably educated on the history of the tartan (thanks, in no small part, to members of this group!) as well as my own readings on the subject.
I understand that tartans were not “officially associated” with specific clans until the late 18th century, after the Highland Clearances. I know that many people feel that it is acceptable to wear any tartan, provided you have at least a little knowledge of that clan’s history.

However, I know there are also quite a few who feel you should not wear a tartan unless you have a direct, “legitimate” lineage to the clan, through the father’s (not the mother’s) bloodlines.

So for those of you with that direct lineage, what is clan affiliation like today? Is there a service done to/for the clan chieftain? What does the clan do for its members? How is wearing the clan tartan different for a “clan member” than it is for someone else? If I were to swear allegiance to a clan chief, what would that gain me? What would my obligations be to the clan?

I pose this question with the utmost respect, and a desire to understand the …fire… that fuels the concept of proprietarial tartans.