I think in the future the previews will be installed with the instruments themselves (at least I thought I read something like that) but since none of the existing NKS supported products have these previews, NI kickstarted everything by shipping every single NKS product's previews. They could have make Kontrol download the files from a server to match the NKS products you have installed/registered. I guess that was too much work or something. So instead they will waste 8gigs of disc space and force everyone to download and install 8gigs of data.
It is interesting in that their are previews for Rob Papen instrument presets that now work for me. If only Komplete Kontrol was resizeable I might actually consider using it.