I've been using XNA for a while to tinker with 2D game development, but I can't help but feel constrained by the content pipeline when targeting PC only. Things like no vector fonts or direct use of graphics files make it a pain while other frameworks do these things with no problem. I like XNA because it's robust and has a lot of support, but what are the specific benefits that I'd get developing exclusively for PC, if there are any at all?
Everything you are complaining about has been solved by the XNA community or is actually supported by the library.
Vector Fonts thanks to the Nuclex Framework
Anyways your main question makes no sense. Why are "specific benefits" for PC developers a desired trait? The library makes 2D graphics very easy on all supported platforms. So no, there are no benefits to being a PC exclusive developer.