I think it's a combination of physics (wavelength is 20x larger than visual light, making optics and sensors trickier) and export control, as you could (literal

I think it's a combination of physics (wavelength is 20x larger than visual light, making optics and sensors trickier) and export control, as you could (literally) weaponize a high-res thermal camera to make an autonomous drone/missile targetting hot exhaust etc.