I think you're missing his point, or I'm missing yours.
Why do clubs like GOAL and the NRA have memberships? They raise money to support their operations.
Why do people join clubs like GOAL and the NRA? To support those operations.
You aren't joining for The Outdoor Message, The American Rifleman, or a bumper sticker. You join to support their operations. They offer Life Memberships to gain a larger amount, and as a convenience to their supporters. They offer Endowment Memberships to allow their supporters to continue to support, even though they "owe" nothing.
Sometimes, a club needs more money fast. What's the easiest way to get it? You can get MORE memberships, which results in you drumming up people for 30 bucks a whack, or you can entice your current membership, who has already established they support your cause, to give you more money. The reduced rate life membership does just that.
What I think Molon.Labe is saying is that if you've chosen to support them, why try to find a way to support them less? He seems to be suggesting that the reason you'd do so is simply because you want to say you're a life member, and the true reason isn't supporting the organization. If you truly supported the organization, you'd just give them money.
I'd never really thought about it that way, but it certainly makes sense.