Most of the people using Microsoft have OEM licence. When people buy new hardware, people are buying a new license of Windows as well.

Customers are typically unhappy when Microsoft refuses to fix critical bugs that only arise when running Windows on older hardware.

To the average user, "Windows installs without error and hardware appears to work" = "Microsoft supports running Windows on this hardware", even if the hardware is EOL and requires drivers that haven't been updated since Windows Vista.

Windows 10 to Windows 11 upgrades are free. You know what's not free? The Windows license on a brand new computer if it's bundled with Windows. And here's a friendly reminder that the vast majority of users don't know how to build their own computer and install an operating system, even if it truly has been made extremely simple nowadays.