The reason we need this is because there's a non-trivial amount of people signing marriage papers for a visa. This happens because basically every other road, for a vast majority of people, is closed, or very difficult.
I am married to another immigrant: We had been a couple for quite a few years before marriage, but we did sign papers right away when, through some strange USCIS situation, a whole lot of visas that weren't going to be processed for years became current. She was still in school, so the green card process wasn't available to her yet. If we got married, she would skip at least 6 years of her own green card process, and it'd not cost anyone any extra. This also meant that she could go to any employer, instead of having to look for one sponsoring immigrants: A huge difference.
If it was far easier to become a US citizen, then we'd not have such pressure to sign papers, either for legitimate marriages or straight out fabrications. But it sure seems that the US has no appetite to, say, triple the employment-based visa caps, which I suspect is as much as we'd need to clear up that side of the system, once we take into account the Chinese and Indian side of the backlog.