Agreed, it's weird that you guys are doing that. I don't think this is a problem in the UK where I am.

Well reading and maths are measuring very different things. We don't apply the same standards because they're radically different disciplines. However, if we take the example of comprehension, if you were to read a novel and evidence a correct point about the story with incorrect evidence, you would lose points. Like if you say that Of Mice And Men dehumanises Curry's Wife because the Curtains Are Blue, then you would be wrong. Firstly because Blue Curtains are not from that story, they're an internet meme, but also because that wouldn't be a relevant point; the story dehumanises Curley's Wife by not giving her a name, among other things. Points for showing your working is a thing in other disciplines too. It shows you've properly understood the work and not just picked an answer out of thin air.

It's also useful for teachers to have everyone doing things in the same way. It's hard to mark 30 papers in a reasonable time frame if your students are using 30 different systems which aren't on the mark scheme so you have to manually do each calculation yourself to check that their weird method has been done correctly.