Why does Capcom use weird proprietary formats for their games?

It makes it harder for other companies to reverse engineer and possibly steal their work. Also, different teams probably created their own formats. There is probably a book inside capcom headquarters that details how each format works.

I get you. I keep fighting with their odd formats. Thankfully I figured most of them.
Resident Evil on Gamecube, Okami on Wii, Capcom VS SNK. So many odd formats I had to extract to finally be able to use.

Is that an audio format? Something there rings a bell.

Anyway three main reasons
1) The devs don't know or want to learn the ones provided by the SDK, this plays especially when using an engine they bought in.
2) The devs reckon they can do a better job than the one provided by an SDK or the devs bought in a format that can do a better job, at least theoretically.
3) Might make reverse engineering harder. I am not sure how many console devs really care about this as there are loads of obvious things they could do that would really frustrate efforts and cost basically nothing (a basic broken pointer table that is regenerated at runtime would hurt things, make a very basic file system that can handle fragmentation and both ROM hackers and asset rippers not using emulators have a far harder time) and I don't see it outside a handful of PC games, see it all the time in other things the devs have a vested interest in not having people other than them understand.

Cause is usually just how they choose to do things, all devs use whatever they see fit. Why does Donkey Kong Country use RAS as a audio file? Why smash bros use BRSTM, when I thought is more common to use ADX, why capcom moved to using unreal engine instead of sticking with their MT framework? It is just as they see fit. Honestly I would prefer the devs to use whatever they actually know how to use and more comfortable with and if they choose to use other stuff to fully understand how to use it before actually using it.

@Sonic Angel Knight it's worse than just different formats.

Files are packed, encrypted, and sometimes compressed, making it difficult to extract, and finally grab usable files.

Thanks to a random person on the interwebs I was able to convert it! I might write a tutorial if anyone is interested.