I don't think the WFBS issue has to do with thriftiness or lack of hardiness. I think it has everything to do with the general decline in interest in the Mediterranean/light Continental type birds, ie, your white egg layers. White eggs are not popular, flighty birds are not popular, skinny birds, not that popular. If you look over this forum, you will quickly see that the dark eggers, blue or green eggers, dual purpose types, and crested, feather footed type chickens dominate, and wild patterns and novel colors. I think the whole thing is a crying shame.
Personally, I think a chalk white egg is thing of beauty, and the Spanish and Minorcas, and Hamburgs, are some the showiest, and thriftiest breeds around. This site seems heavily biased to "pet" chickens also, so it's not the best place to gauge the worthiness of a breed. A lot of great old productive breeds get forgotten in the face of a crested lavender laced olive egger.