I like hacking because, well, it's something I find very intriguing. Being able to modify a game to do things it was once not able to or visually changing something such as graphics is just interesting to me. Well, actually, I think there's a lot more to it than that, and I'll explain it.
As time moved forward, more and more tools (such as Emblem Magic, FEBuilder, and Buildfiles to name a few) came along to make this small hobby much more accessible to those who were too intimidated at first, myself included.
The Hacking Community
As much as I like making minor changes such as a map or event for a joke or two between friends, I like seeing others hack as well. I know that a few may not agree with some of these, but events such as FEE3, PMEs (Pick My Edits), MAFC, Chapter/Resource Blitzes, and Ragefest (the list goes on, trust me) are more or less a collage of talents from different people who happen to share the same hobby, be it a contest or collaboration effort. I've also met some great friends through this, so I have my personal thanks to throw in for that.
I believe another thing I like about hacking is that Fire Emblem itself is a goldmine of (nearly) infinite possibilities and potential, and many people see that. The various mechanics introduced throughout the series' history are something that a few brave souls dared to implement to the GBA titles, such as the skill system, Pairups (into FE8), and Quality of Life changes to name a few. That isn't all, either. There's also original mechanics that were implemented as well, such as leveling down, or even ice puzzles. I recommend looking into the list of things I listed in the second spoiler (The Hacking Community) to get an idea of what I mean.
Although I did not say much about FE6 or 7 here, that doesn't mean they don't play a large part even today. There are people who do work in these games as well, two big examples being Maiden of Darkness (FE6) and Elibean Nights. There may be more support for one thing over the other, but that doesn't stop some from doing what they love.
There's no way I could leave this out without feeling dissatisfied. Besides the normal ROM hacks, there's quite a few engines that were made to simulate FE with varying results. FEXP, Lex Talionis, and FEXNA (2020? Let's pray) are just some I can name off the top of my head. There was also a new one introduced here not too long ago as of writing this, which is pretty cool.
If you've been around the block a few times, you know what a randomizer is. It mixes up various aspects of a game to create a different experience. A lot of people find fun in this, as it gives them a reason to go back and play their favorite titles that have a program made to do this. Circleseverywhere managed to do this for FE8: a self-randomizing hack, which, as the name would imply, allows you to randomize FE8 without anything other than applying the patch itself, which means you don't need a new rom for every playthrough.
Revisiting Old Relics
This one may be even more rare (and for novelty in some people's eyes), but let's be real here: how would you feel if someone went outside of the normal routine of hacking FE6-8 and did something like... FE5, Or even FE1? It's really impressive. They went out of their way to do something with probably minimal tools/documentation, and that is both respectable and admirable.
A short FE1 hack by Darrman (For MAFC 3)
A concept for FE7 in FE5, by Zane Avernathy (For FEE3)
Translations and Translators
I don't know if anyone thought about this one, but I include translations with all of this as well. It's a very important part of Fire Emblem's history (that includes the Tear Ring Saga series), as it lets us see the content that would otherwise be lost behind the language barrier. Props go out to folks like Bookofholsety for being awesome. Yes, before some of you say it, there's a few translations out there that are subpar, but we have to start somewhere. If anything, I consider those a base for future translators to further work on/use as an example of what NOT to do when proceeding, that being errors that can freeze the game (hi Thracia 776), or glitchy text.
An FE5 Menu Translation
Project Naga's FE4 Translation
This also includes non-official material. we got a menu translation for FE Girls and FE Midori (the second of which spawned inspiration for REDFE by Mystic, be sure to check that out, it's cool.)
You may asking what I count as "foreign" here, and that would be non-english speakers. Nothing to do with where you are in the world, but the language you speak, but I digress. We usually get some folks from other places, such as 7743, the creator of FEBuilder. If you look around long enough, you'll see others as well, and it puts a smile to my face to see them communicate. We can learn from them, and they can learn from us.
Something to Put Out There
It doesn't always have to be about quality:tm:, really, but just an end result that shows someone out there was, or still is, hopefully, passionate about hacking Fire Emblem. This could either be an expansion to an already existing tale, a crossover of sorts, demakes, or to present new ideas altogether. The motives of these individuals can vary (for fun vs for glory), but at the end of the day, it's just a thing people do.
I may have missed some things, but these are the reasons why I like hacking, some less so for why I personally hack, and more so what I like about the hobby as a whole.