Again, I am arguing devils advocate because I would be quite unhappy with increased forearm regulation - I live in a very rural area where firearms are a tool and a cultural artifact, and I like them.

With that said - almost nobody goes through the trouble of manufacturing anything. Making it difficult to access firearms means that most people who might think about getting a gun will just get something else. Your opponents not having a gun also makes you less likely to feel like you need one.

I won't argue that it's possible to deter a sufficiently motivated person, but most people are not that motivated. Making undesirable things 'uphill' is pretty effective.