Tech is has one of the best combinations of (lucrative + meritocratic) I've seen. Fields that pay similarly or better (law, medicine, investment banking) require either significant time-consuming credentials or significant time investment as an underlying (like IB analyst).
The interview process does require intensive preparation to land a top spot. However, your compensation package increases proportionately to the preparatory time. From the mind of a top performer, wouldn't you want to seek out the best of the best, rather than settling for median wage? It seems like unionizing will encourage the top workers to leave while the below-average to stay, dragging down the overall talent pool.