I've read countless papers on crypto, and they mostly seem pretty formal to me - what are people comparing them to? Is it really worse in other fields? There is some variation - DJB's style is distinctly less formal than other authors - but my perception is that papers on for example network engineering seem a lot less formal than crypto papers. I think there's plenty of room to improve the readability of crypto papers by encouraging less formality.

One trivial example of signalling here is the way everyone still uses the Computer Modern font. This is a terrible font, and it's trivial to improve the readability of your paper by using, say, Times New Roman instead, but Computer Modern says that you're a serious academic in a formal field.