It has lower wages because workers doing the same jobs as in the United States are less productive. Even a Mexican worker doing the same work on the same machinery as a U.S. worker is less productive. That's because of other factors. Roads are not as good as in the United States, which drives up transportation costs. The banking system is broken.
Financing costs are higher.
Mexico's legal system often issues rulings based not on the facts or the law, but on who you know. That reduces the certainty of contracts, and there's nothing businesses hate more than uncertainty. Education is not as good. But with job and population growth getting into balance, all that will change. They said the agreement would cause our living standards to merge.