Can you use twisted wire instead of coaxial cable?

It is cheaper.

When a signal is passed through a wire, some of that energy is radiated out into the air. That signal can cause interference with other receivers. By twisting the wire along the entire path, the signals get canceled and do not interfere with other receivers. As the frequency increases and the wavelength gets shorter, more of the energy is lost and can cause interference, even though the wires are twisted.

At high frequencies the central wire is completely surrounded by a metal covering. None of the signal can escape. This wire is much more expensive.