The reason we never bother to list neck weights is because it rarely comes up as an concern point for customers. If someone gets a super extra light hollow body and is concerned about neck weight, they generally know to shy away from heavy neck woods. But even if they don't, they rarely experience a problem. Even if they have head dive, that does not effect a good portion of guitar players since some of the most famous OEM guitars are naturally that way.
So, do we go out of our way to start weighing every neck to sensitize people to an issue that normally has little consequence and perhaps detours them from trying out an exotic wood that may have ended up their favorite? Being a fan of exotic wood necks myself, that would be a shame. I know some people really take a leap of faith trying new and different neck woods and designs and are so glad they jumped afterwards. I would hate to put a "perceived" speed bump in their way.
If weight is especially important to you when buying a Showcase neck, ask your rep to weigh it for you. Otherwise, I don't think I can come up with a compelling reason to have (the already stretched) Warmoth resources pointed at keeping track of neck weights. That doesn't mean sometime in the future it won't happen, it just means we have many other initiatives at the top of the priority list currently. Like, anyone know a CNC programmer that wants to work in a guitar factory?