In spite of the fact that music schools are churning out staff-and-blot literate musicians at an unprecedented rate, and that the expectation of literacy for professional popular musicians has never been higher, it is probable that a fully functioning staff view is not a priority for most Sonar customers. I expect that most buyers are not going to manuscript paper and pen as their preferred method of capturing a musical idea. After years of unrewarded hoping for a staff view that would work superbly either as input or output, I have pretty much given up. Amateur loopsters and wannabee professionals with more interest in stardom than discipline drive the market for this kind of software. Many more wallets will open for a step sequencer than for a staff view. For most users Sonar is a recording device or a musical instrument, not primarily a method of preserving music for the post digital age when flesh-eating rappers rule the streets and computers can only show cat videos.
As for classical/unpopular musicians, well you chose to walk a higher path. Don't expect the masses to support your needs, or those who take the masses cash to pay you your well-deserved respect if it costs them money.
I was able to pick up Notion for about 50 bucks on sale for integration, and you can get Lilypond free if you need a pretty printer.