Like everything else, it probably comes down to quality. You can't expect something that costs $40 to be extremely accurate down to the thousandth of an inch. It would be nice, but it's not realistic.
I have a digital I have been using for years, but I dont like having to run out and buy batteries every year, and it's quite finicky. I have been slowly reverting back to non-digital, and rarely if ever use the digital one now.