Paying Apple One monthly for 12 months is still cheaper than subscribing to the annual versions of the various services.Apple probably doesn't offer it because people would find out it is cheaper to pay for music yearly than paying the monthly price. The same is true for AppleTV+ and probably Fitness+ as well.
For people like me who don't use the arcade etc., it wouldn't be but, that is good to know if at some point, I decide to make use of every offering.Paying Apple One monthly for 12 months is still cheaper than subscribing to the annual versions of the various services.