I don't collect them, but I enjoy reading about them.
There's the element of military strategy and importance, and also the cultural and historical aspects are interesting. St. Helena is featured on the back page of the latest APS magazine.
I don't own any of the SG catalogs -- I've been tempted by a few of them, not because I collect, but just because I'd like to read them and learn. I could convince myself to pay the purchase price, but the currency exchange is working against me and I just can't bring myself to pay the £8 or £9 shipping to the USA.