I think I'm not understanding what comparison you're trying to make. I thought you were expressing some doubt about whether H1B, or temporary skilled worker visas generally, were beneficial for the host country. You asked, "why don't other countries encourage this specific type of immigration" and I pointed out that they do have similar programs. Now you ask "why don't they have even higher rates of skilled worker immigration?"

Japan's SSW program has close to 300k workers. The U.S. H1B program has about 700k workers, so by population, Japan's program appears to be a bit larger. New Zealand's AEWV program has 80k workers with a population of 5 million so proportionally that's much larger.