Industry wants to make a lot of product, quickly, at a low cost. The conditions in a factory are chosen to give an acceptable yield in an acceptable time without costing too much. This often means a compromise.
Cost depends on the raw materials and the energy supply. In the Haber process, nitrogen is almost free because it comes from the air. Hydrogen costs more because it is made from natural gas. Heating the reactor and compressing gases to a high pressure both need a lot of energy, and a plant that can survive very high pressure is expensive to build. Recycling the unreacted nitrogen and hydrogen means less is wasted, which saves raw materials.
The forward reaction in the Haber process gives out heat. A very low temperature would make the yield of ammonia increase, but the reaction would be far too slow. A higher temperature makes it fast, but the yield falls. A temperature of 450 °C is a compromise. The iron catalyst lets the reaction reach equilibrium quickly at this moderate temperature, which saves energy.
A higher pressure gives a higher yield because there are fewer gas molecules on the right of the equation than on the left. But very high pressures cost too much. A pressure of 200 atmospheres gives a worthwhile yield at an acceptable cost.