Linux kernel can boot mostly on its own by probing the hardware and using the linked-in drivers. The NT kernel requires an environment such as UEFI or legacy BIOS and relies on it, for example, to load additional drivers. It also expects to be loaded in a certain manner by the pre-loader (winload.efi) while Linux has less strict requirements. 

This is why QEMU can provide built in support for booting Linux - it’s much simpler to implement. For Windows you need to prepare a disk image with the file system and a UEFI environment such as OVMF. The Windows kernel uses registry (BCD - Boot configuration data) for configuration instead of command line arguments so it’s trickier to implement.