EUV is all about the laser. To create the small transistors of 4nm for example, either lithography or some other laser tech, you need to be able to shine a pure light on them of small enough wavelength. EUV is the smallest we can create thus far.
I suppose that the real issue is that EUV is the smallest we can focus thus far. Otherwise we'd be using harder X-rays from things like synchrotron light sources, no?
