Source: Microsoft
Microsoft wants to focus its resources on the latest generation consoles instead of producing the older Xbox One models. The company has announced it will focus on making more of the still-scant Xbox Series X/S models. Microsoft already stopped producing the Xbox One X and Xbox One S All-Digital Edition in 2020. Now, the manufacturer won't make any other variant of the Xbox One series. Any of the Xbox One models you see in the market are existing stock.
Sony is taking a different approach to Microsoft, opting to continue producing PlayStation 4 units this year to fill the lack of the PS5 stock. The Xbox Series X/S and PS5 still quickly sell out when new stock is announced, so we can't say if these strategies will pay off.