Kindle format isn’t just for Kindle hardware, if you have an iPad you can read it, so it’s probably aimed at people who have larger format devices running the Kindle app.
As another poster mentioned, you can use the kindle software on other devices. I have it on my surface (larger screen), and on my Windows 8 desktop.
Using a touch screen for sheet music actually was possible before this as well. I seem to remember an article where Harry Connick Jr had a patent submitted for his big band podiums where the sheet music was displayed electronically and could be “paged” wither through touch or timing as well.