Microsoft has increased the minimum storage capacity required by Windows 10 to 32 GB. Previously, it was 16 or 20 GB. This change affects future versions of Windows 10. Updated May, 2019, also called version 1903 or 19H1.
Prior to this update, 32-bit versions of Windows required at least 16GB of storage on your device, while 64-bit versions of Windows required 20GB. Now both will need 32GB.
It's unclear exactly why Microsoft made this change. The update of May 2019 now reserve about 7 GB of your PC's memory for updates, so it may take more space in general.
Let's be honest though: you've always wanted to have more than 16 GB of space for Windows 10. Microsoft wanted Windows 10, like Windows 8 before, to work on tablets and lightweight laptops with little storage. These light devices often had a compressed operating system and had trouble upgrading to Windows 10.
Although this seems like a big change, it really is not the case. You should have avoided devices with this ridiculous amount of storage because they would not have worked properly with Windows 10. Microsoft now makes it official. Microsoft PC partners can no longer try to sell laptops and tablets with less than 32 GB of integrated storage. This is good news for buyers.
If you are using a computer with less than 32GB of Windows 10 storage, we do not know what will happen to your device. It may never receive an update of the May 2019 update (version 1903). It's up to Microsoft.