kontakt is pretty much their flagship product.. it's down to the sample makers to make their libs compat. with kontakt player etc. you can't find alternative sample libs?? you don't state the ones you have issue with.
if it's NI libs, then of course they want you to buy the full thing.. it's their "want" item, sorta like logic... but you need a mac to run it..
much like 1001 pro audio things... e.g. even sonar producer has things studio doesn't.