Hi Molly,
Nothing in your post is silly; it reflects sound analysis. I do not believe we will ever see legalized standard capacity magazines again due to the viciousness of politics. The minute such a debate were to be brought to the floor, Feinstein, Boxer, Schumer, et al, would launch a tirade about how their opponents lack caring for crime victims. They would argue that the current law is working as intended, and they would produce cooked stats in support of their lies. Further, they would argue that it's irresponsible to put our kids in danger as a result of legalizing standard capacity magazines. If perchance they were to once again become legal and God forbid a shooting occurred in which a standard capacity magazine was used, the liberals would hang freedom-loving legislators out to dry by asserting that were directly responsible for the tragedy.
This legislation was foisted upon us by deceit. We need to have legialators prove that standard capacity magazines were actually responsible for criminality. Obviously, an inanimate object is incapable of forming the intent to do anything. We must force our legislators to prove to us that individual responsibility is not the cause of crime, that standard capacity magazines are. Then we must make them prove efficacy of their legislation; that they are able to eliminate all confounding factors leaving standard capacity magazines as causal of said efficacy. I would love to see them attempt to prove that their legislation is even remotely responsible for a reduction in crime vis-a-vis three strikes legislation.
Forgive me, Molly, for my tangential response, but this is an issue that pisses me off to no end! I have been a practitioner in the criminal justice system for nigh on two decades, my undergrad major was CJ, I have been exposed to scholary research on gun control, and my no-so-expert opinion is that there is no there there. However, there is there there when one considers a hidden agenda for our eventual disarming. Check out John Lott's "More Guns Less Crime;" it's excellent scholary research on this topic. He explicates his research methodology and supports his thesis with facts. Unlike his attackers and supporters of gun control, Lott's work is devoid of emotion and hidden agenda.
What would make my day is the voting out of office of all those lying bastards (and bitches) responsible for the eroding of our precious freedoms. Then I would like to see almost all of these laws either repealed or have the US Supreme Court rule that they are illegal. I do fear a government that fears its citizens owning arms. As a cop, I have never feared a law-abiding citizen owning a gun; however, I have deeply rooted fear of criminals, with or without guns! Molly, your owning a standard capacity magazine is of little concern to me; criminals are: and you should have at your convenience the best means possible to protect your family and yourself from those on the outside of law.
So, in answer to your question, I believe that manufacturers have retained the configuation of certain models of their guns due to engineering and manufacturing costs. It's just cheaper to modify a magazine than it is to redesign a new model; and there might be an attendant marketing gimmick as well. People might feel better about buying a gun for which it is possible to use a standard capacity magazine.
Best of luck,
E