For me, the "why" is that I grew up playing RPGs, and around my early teens I discovered the west missed out on dozens of major games (even Dragon Quest 5 and Final Fantasy 5!)
I taught myself programming and reverse engineering so that I could fan translate these games.
After I finished a few of them, I became disheartened that my work had trouble running on real game consoles due to emulator inaccuracies.
The folks writing emulators at the time took many shortcuts to run on the slower computers we had back then, but in spite of PCs getting faster, they didn't want to incur any speed hits or break any other fan translations relying on emulator bugs.
So I switched focus and started writing my own emulators instead. I was filling a niche that at the time wasn't covered. These days, I mostly keep at it because it's fun, I like the games on these old systems, and I'd like to preserve the games for future generations as faithfully as possible.
(if you're bored and would like a really in-depth answer, see https://byuu.org/about for a full history.)
I taught myself programming and reverse engineering so that I could fan translate these games.
After I finished a few of them, I became disheartened that my work had trouble running on real game consoles due to emulator inaccuracies.
The folks writing emulators at the time took many shortcuts to run on the slower computers we had back then, but in spite of PCs getting faster, they didn't want to incur any speed hits or break any other fan translations relying on emulator bugs.
So I switched focus and started writing my own emulators instead. I was filling a niche that at the time wasn't covered. These days, I mostly keep at it because it's fun, I like the games on these old systems, and I'd like to preserve the games for future generations as faithfully as possible.
(if you're bored and would like a really in-depth answer, see https://byuu.org/about for a full history.)