That means you could theoretically edit/fix a broken stl file by hand. If you knew what to look for.
I've used ascii formats in the past for animation production purposes. I would get my scripts to read in and edit files in our content directory. This was Maya ascii files, but binary vs ascii should be the same.
I doubt you would need/want to do something similar for 3d printing. Like Dan said , binary is compressed, so I'd stick with that.