Does Amazon Category really matter?

I have around 70 products, all within a similar category. For some unknown reason Amazon keeps changing the category of my products to something irrelevant – for example, if I have a birthday card, they put it in the gift box or diary section. I keep changing them to the correct category and then a few months later, they are changed back. It’s a complete waste of time and I’m getting nowhere with amazon (lack of) support. So, should I just give up? Will having my products in the wrong category really affect my business?