I think that many bluegrass musicians with years of playing experience have a keen interest and deep respect for various forms of folk music. This comes about by knowing where the music roots are when you search out the music. There are for example old time musicians that are techincally capable of playing bluegrass music as well on a professional level and visa versa- e.g. such as Art Stamper, Kenny Baker, John Hartford, Tim O'Brien, Mike Seeger and many others who understand profoundly the music and it's roots and are also not afraid to take the music in new directions as well. Some of the great young players I know around where I live are certainly opening up these days and respecting other forms of music and the musicians who play. Chalk it up to experience of playing music with others informally, or perhaps performing at music camps and festivals where all forms of music gather in one place.
A lot of bluegrass musicians and audiences are focused in only their world only as a choice - be it a matter of lifestyle , taste, or perhaps non exposure and appreciation for other forms of music. You could say the same is true in musicians and audiences of other genres as well.
Tradition - a big part of bluegrass no doubt. How many times to we hear the same Gospel songs, or Scruggs tunes, or Bill Monroe classics over and over from bands. It can get a bit tedious, unless you are ingrained in the culture of bluegrass. Good bluegrass musicians know this and are reaching out in new ways - and they sell lots of records in compared to most folk music recordings.
Have a good read of Ron Block's IBMA Keynote Address on "What is Bluegrass" http://www.ronblock.com/ibma.keynote.2004.html
Arnie Naiman