Now that’s a smart question. Belt-drive turntables are much cheaper to make.
Even small manufacturers can tool up to make a basic belt-drive turntable. You could just about make your own at home and that’s how many small manufacturers start out.
Direct-drive turntable manufacture is quite different though. It requires considerably more engineering and capital investment. Motors tend to be custom-made and need more than just a capacitor to drive them. There are benefits of course, but to the average person wanting a cheap turntable, these extra costs don’t make for cheap turntables.