I flew the A-10. It didn't have anti-ice of any kind. I flew it in the Northeast part of the US. In the winter. In cloud. We'd have ice forming on the gun, the wings, the bombs for God's sake. Anti-ice saves compressor blades (yes. We damaged them) and makes pilots feel better. Beyond that, I'm not so sure. I also flew the C-5 without wing anti-ice for hours in the ILS pattern, in winter, in clouds, never saw much wing icing. Big wing, not so much of a problem.