As well as showing that the sail is class legal, the sailmakers "buy" the buttons from the ILCA, so by buying a new sail, you are helping to support the class association.
Interesting theory. If they are filled with gold (or diamonds, caviar etc.) I may ask the store to cut out the button, to save weight. Doubt I'll get a discount.
Blah, Blah, Blah...before you spew off the same old mantra search the forums this has been discussed several times before. To put things in perspective a new Finn Main is $1,100, a new Optimist main is $580! and new 470 main is $930 and Jib is $490. Of course you can buy a non class legal POS intensity "training" sail for a lot cheaper but a) you can't race with it, b) you can't really call it training because it is different then a class legal sail so when you do race with a real sail it will be totally different the the POS intensity c) you fail to support you class...