With all the news about web fonts lately, I've been thinking about typography as a difference between web apps and desktop apps. No one expects web apps to conform to any standard UI, so designers can experiment and give us distinctive interfaces, using different fonts and color schemes.
It seems like there's less room to play in desktop apps - you'll see unique interfaces with new button styles, new controls, different color schemes, but as far as I can tell, not much variation in typography.
The only example off the top of my head is Panic Sans, used in Coda.
Why so little variation?
Is it the presence of a standard system font, UI guidelines, or just habit?
Is there a licensing issue for redistributing fonts with software? I tried to look for licensing terms, but this doesn't seem to be a common question.
I wouldn't mind some more tasteful variation in my desktop apps - I think the best web apps have shown us that different isn't always bad.