I know a few of the best sources tell us this, and I can't defend them, but it's very much less than the whole story. I believe an early Apple model described a 72 dpi monitor at one time, back before screen dimensions were adjustable, and we're stuck with it now, even without other evidence. There is nothing we can do with that number. For one thing, monitors vary today. Reset the same monitor to different screen sizes, and we get different numbers.
Monitors vary, and the horizontal size control even changes it too.
More pixels in the same area, smaller pixels. There is no reason to abandon the better graphics size just because the fonts are too small. 72 dpi is not a very common result. An 800x600 pixel screen would have to be 11.1 inches wide to show 72 dpi, but the largest 15 inch I have seen is about 10.8 inches wide. A 14 inch 640x480 pixel screen that is only 8.9 inches wide would do it, but it would have to have inch of black border on both sides.