Another reason is magnify-ability, or zoom in-ability. Authors are annoyed when they produce a graphic, and then include it in a document, say expanded to 120% of its original size or shrunk to 75%, and it contains jaggie letters. Similarly, readers are annoyed to blow up a map and find that the town names are hard to read.

Still another is that one set of fonts will do for essentially all documents, so on your hard drive you don't need a set at 10 pts, another set at 11, etc. The space these take up is less of an issue than it used to be, but it is an administrative annoyance.

Another issue impacted me a lot since I put stuff up for download. You have to maintain a number of outputs for the dpi-ness of various output devices, so that people reading on a screen use a different output file than people using a printer. In addition, Knuth has settings called things like blacker to tune the output for the physical output device engine, so you may want to maintain output file versions tuned for a number of different vendor's devices. Besides, at some point printers just became vector devices.

Basically, the market has spoken.