Class, congratulations we've made it to the end. While a technician may be able to work on and even fix certain things without any "firearm theory" knowledge, they would definitely benefit from having that knowledge. The more knowledgeable a person is the better equipped that person can be for any issues they come across. Having the knowledge of how firearms work will greatly benefit someone who is tasked with repairing those firearms. This is all the more evident when it comes to sales. If the salesperson shows knowledge and appears actually interested in what they are selling then potential buyers will be more likely to trust them and go to them for a sale. Knowing what a gun is or the caliber of it may make a person able to make a few sales but if the sales person is very familiar with the inner workings of the firearm and others like it they will be able to better understand what the buyers need or want. Also when it comes to customizing firearms having that knowledge of the physics and how the guns work will be vital for a smith's ability to know what can and cannot be done to a firearm without damaging the actual function of it. If you just start taking away material with a dremel (we've all seen someone do it) then you are bound to run into reliability issues if you don't break the firearm altogether. Understanding "firearms theory" isn't strictly "necessary" but it is important for anyone who wants to succeed when it comes to working on or with firearms.