It is not just bag patterns that are like that. I have been making dolls for longer then I care to admit, and they have pretty much always been printed on regular paper, unless you buy from one of the major companies. And any square or rectangular parts were just dimensions. I use typing paper if the pattern is small enough or freezer paper otherwise. I also like to make the patterns out of heavy interfacing if it is something I want to last. They used to make pattern paper and an interfacing product made specifically for copying off your patterns. When making things for my kids or grandkids, if it was a pattern I knew I would use a lot, or want to use several of the sizes in a multisize pattern, I always copy it off. For some strange reason I have always found that process relaxing.
I only use my rotary cutter for quilting or sometimes bags. I don't think cutting through tissue onto fabric would be very accurate. But I could be wrong.