You only have to do this important job with masking tape once to understand what I am talking about.
One reason that utility grade masking tape is so inexpensive is that it uses a very low quality adhesive. This rubber resin based adhesive has good holding power when it is fresh, but dries out very quickly. When this happens, the adhesive separates (de-laminates) from the paper backing. The paper can be lifted off, but the dried out adhesive stays behind.