Why is there always a tendency to oppose a change in magnetic flux? Why doesn't the loop reinforce the change instead?

If it reinforced the change our moving bar, after receiving a tiny push from us, would pick up speed all by itself. This makes no sense from a conservation of energy perspective. Opposing the change, on the other hand, conserves energy. With the bar the initial kinetic energy is dissipated as heat. To keep the bar moving requires an applied force to overcome the opposition of the loop.