Comment by m132

These days, as most take 1x scaling factor for 96 PPI (or 72 if you're Apple), yes, but at the very beginning, there was no such reference. 100x100 without the density could have meant 10x10 or 100x100 inches.

Some software, most notably image editors and word processors, still try to match the zoom of 100% with the physical size of a printout.