Looking at replacing my cabin base and was surprised to learn AF & KLM only permit hand luggage widths of 35cm (55 x 35 x 25).

I've never seen any cabin baggage checked and doubt a 40cm wide case would cause any issues whatsoever. But just thought I'd put it out here to see if anyone knows why its only 35cm and if there's a reason I should avoid buying a w40cm case?

Only checked because the case I planned to buy didnt have KLM as a compatible airline yet had all every other flag carrier I would typical use and all low cost carriers I would likely use.