Well, tech cam makers in general are like 10-15 years after when it comes to internet visibility. Arca-Swiss is not the only one with a rarely updated rudimentary web, just look at Linhof, Cambo, Silvestri etc. I don't think it's about that they can't afford having a nice web, it's simply because they don't think they need it.
For the current size of the companies I don't think they really need any strong web presence, the dealers take care of that. However if they want to grow their business and reach more people a great web would not hurt.