Skilled tradesmen (and women) are going to hold a lot of sway in this fight. They were already hard to find before. Cutting your pool in half will make it even harder. Employers can't just train up whole new crews on the spur of the moment from the vaxxed without taking major hits. Not to mention that people who simply got vaxxed because someone told them to are not the kind of people these employers are going to want. Working with complex machinery and techniques often leads to situations that require innovation on the fly and not waiting for someone to tell you what to do.