The Nazi regime did experiment and produce poisonous gases, but they ultimately determined that the use of these gases would prove to be more trouble than they would be worth.
One of the main reasons that the Nazis did not use poisonous gases on a large scale was because they feared retaliation from Allied forces. The Allies had signed the Geneva Protocol in 1925, which banned the use of toxic gases in warfare, and had explicitly warned Germany about the consequences of breaking this agreement.
Furthermore, the use of poisonous gases in open warfare was also seen by the military leadership as being inconsistent with their tactical objectives. Gas was considered to be relatively ineffective in battle, as it could be dispersed by wind or weather conditions and could be prevented by the use of protective equipment.
Additionally, the production, transport, and delivery of gas would require significant financial and logistical costs, and the use of gas could potentially harm their own troops as well as civilian populations.
Lastly, while the Nazi regime was prepared to take extreme actions in order to achieve their objectives, the use of poison gas on a large scale would have been globally condemned and led to significant repercussions.
In conclusion, while the Nazi regime did experiment with the production and use of poisonous gases, they never used it on a large scale against enemy soldiers during the war. The reasons for this decision were due to several factors, including concerns about retaliation, the perception of the weapon's effectiveness in battle as well as the logistical and financial costs associated with its use.