Let's imagine you are an embedded programmer and you want to play with some kind of LCD screen. You want to print some text and that is suddenly hard, because you can only draw pixels. You can't use .ttf fonts because you have no OS in your device (and even if you have, it might have no concept of 'files' alltogether). So you have googled something like "bitmap fonts for embedded lcd screen arduino" and whooaa that's really a lot of them! And of course none of them is acceptable. It's always like that. Maybe you need 5x7 font but all you see is either 5x8 or 6x7. Maybe you are looking for non-latin font. Or maybe you are dealing with something like MAX7456 for making OSD overlay and suddenly you need two bits for each pixel, not one. Or maybe you need three bits for each pixel. Or four.