I have 3 Apple devices but iCloud is limited to 1 account why?

When Apple sells devices it includes the cost of 1 iCloud account for each device. Many Customers who buy apple products usually have more than 1 device. I own 2 iPhones and 1 iPad and plan to buy a Mac. If I want them all to sync I need to use same Apple id but I get free space for only 1device when I have paid for 3 devices. Apple needs to change its policy as this is an irritant and definitely not customer service. It’s a minor change in the iCloud software